D21315.diff
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	diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
	--- a/src/__phutil_library_map__.php
	+++ b/src/__phutil_library_map__.php
	@@ -218,7 +218,7 @@
	'ArcanistGitAPI' => 'repository/api/ArcanistGitAPI.php',
	'ArcanistGitCommitMessageHardpointQuery' => 'query/ArcanistGitCommitMessageHardpointQuery.php',
	'ArcanistGitCommitSymbolCommitHardpointQuery' => 'ref/commit/ArcanistGitCommitSymbolCommitHardpointQuery.php',
	- 'ArcanistGitLandEngine' => 'land/ArcanistGitLandEngine.php',
	+ 'ArcanistGitLandEngine' => 'land/engine/ArcanistGitLandEngine.php',
	'ArcanistGitLocalState' => 'repository/state/ArcanistGitLocalState.php',
	'ArcanistGitUpstreamPath' => 'repository/api/ArcanistGitUpstreamPath.php',
	'ArcanistGitWorkingCopy' => 'workingcopy/ArcanistGitWorkingCopy.php',
	@@ -288,7 +288,11 @@
	'ArcanistKeywordCasingXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistKeywordCasingXHPASTLinterRuleTestCase.php',
	'ArcanistLambdaFuncFunctionXHPASTLinterRule' => 'lint/linter/xhpast/rules/ArcanistLambdaFuncFunctionXHPASTLinterRule.php',
	'ArcanistLambdaFuncFunctionXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistLambdaFuncFunctionXHPASTLinterRuleTestCase.php',
	- 'ArcanistLandEngine' => 'land/ArcanistLandEngine.php',
	+ 'ArcanistLandCommit' => 'land/ArcanistLandCommit.php',
	+ 'ArcanistLandCommitSet' => 'land/ArcanistLandCommitSet.php',
	+ 'ArcanistLandEngine' => 'land/engine/ArcanistLandEngine.php',
	+ 'ArcanistLandSymbol' => 'land/ArcanistLandSymbol.php',
	+ 'ArcanistLandTarget' => 'land/ArcanistLandTarget.php',
	'ArcanistLandWorkflow' => 'workflow/ArcanistLandWorkflow.php',
	'ArcanistLanguageConstructParenthesesXHPASTLinterRule' => 'lint/linter/xhpast/rules/ArcanistLanguageConstructParenthesesXHPASTLinterRule.php',
	'ArcanistLanguageConstructParenthesesXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistLanguageConstructParenthesesXHPASTLinterRuleTestCase.php',
	@@ -320,9 +324,13 @@
	'ArcanistLowercaseFunctionsXHPASTLinterRule' => 'lint/linter/xhpast/rules/ArcanistLowercaseFunctionsXHPASTLinterRule.php',
	'ArcanistLowercaseFunctionsXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistLowercaseFunctionsXHPASTLinterRuleTestCase.php',
	'ArcanistMercurialAPI' => 'repository/api/ArcanistMercurialAPI.php',
	+ 'ArcanistMercurialCommitMessageHardpointQuery' => 'query/ArcanistMercurialCommitMessageHardpointQuery.php',
	+ 'ArcanistMercurialLandEngine' => 'land/engine/ArcanistMercurialLandEngine.php',
	+ 'ArcanistMercurialLocalState' => 'repository/state/ArcanistMercurialLocalState.php',
	'ArcanistMercurialParser' => 'repository/parser/ArcanistMercurialParser.php',
	'ArcanistMercurialParserTestCase' => 'repository/parser/__tests__/ArcanistMercurialParserTestCase.php',
	'ArcanistMercurialWorkingCopy' => 'workingcopy/ArcanistMercurialWorkingCopy.php',
	+ 'ArcanistMercurialWorkingCopyRevisionHardpointQuery' => 'query/ArcanistMercurialWorkingCopyRevisionHardpointQuery.php',
	'ArcanistMergeConflictLinter' => 'lint/linter/ArcanistMergeConflictLinter.php',
	'ArcanistMergeConflictLinterTestCase' => 'lint/linter/__tests__/ArcanistMergeConflictLinterTestCase.php',
	'ArcanistMessageRevisionHardpointQuery' => 'query/ArcanistMessageRevisionHardpointQuery.php',
	@@ -524,6 +532,7 @@
	'ArcanistWorkflowArgument' => 'toolset/ArcanistWorkflowArgument.php',
	'ArcanistWorkflowGitHardpointQuery' => 'query/ArcanistWorkflowGitHardpointQuery.php',
	'ArcanistWorkflowInformation' => 'toolset/ArcanistWorkflowInformation.php',
	+ 'ArcanistWorkflowMercurialHardpointQuery' => 'query/ArcanistWorkflowMercurialHardpointQuery.php',
	'ArcanistWorkingCopy' => 'workingcopy/ArcanistWorkingCopy.php',
	'ArcanistWorkingCopyCommitHardpointQuery' => 'query/ArcanistWorkingCopyCommitHardpointQuery.php',
	'ArcanistWorkingCopyConfigurationSource' => 'config/source/ArcanistWorkingCopyConfigurationSource.php',
	@@ -1298,8 +1307,12 @@
	'ArcanistKeywordCasingXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
	'ArcanistLambdaFuncFunctionXHPASTLinterRule' => 'ArcanistXHPASTLinterRule',
	'ArcanistLambdaFuncFunctionXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
	+ 'ArcanistLandCommit' => 'Phobject',
	+ 'ArcanistLandCommitSet' => 'Phobject',
	'ArcanistLandEngine' => 'Phobject',
	- 'ArcanistLandWorkflow' => 'ArcanistWorkflow',
	+ 'ArcanistLandSymbol' => 'Phobject',
	+ 'ArcanistLandTarget' => 'Phobject',
	+ 'ArcanistLandWorkflow' => 'ArcanistArcWorkflow',
	'ArcanistLanguageConstructParenthesesXHPASTLinterRule' => 'ArcanistXHPASTLinterRule',
	'ArcanistLanguageConstructParenthesesXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
	'ArcanistLesscLinter' => 'ArcanistExternalLinter',
	@@ -1330,9 +1343,13 @@
	'ArcanistLowercaseFunctionsXHPASTLinterRule' => 'ArcanistXHPASTLinterRule',
	'ArcanistLowercaseFunctionsXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
	'ArcanistMercurialAPI' => 'ArcanistRepositoryAPI',
	+ 'ArcanistMercurialCommitMessageHardpointQuery' => 'ArcanistWorkflowMercurialHardpointQuery',
	+ 'ArcanistMercurialLandEngine' => 'ArcanistLandEngine',
	+ 'ArcanistMercurialLocalState' => 'ArcanistRepositoryLocalState',
	'ArcanistMercurialParser' => 'Phobject',
	'ArcanistMercurialParserTestCase' => 'PhutilTestCase',
	'ArcanistMercurialWorkingCopy' => 'ArcanistWorkingCopy',
	+ 'ArcanistMercurialWorkingCopyRevisionHardpointQuery' => 'ArcanistWorkflowMercurialHardpointQuery',
	'ArcanistMergeConflictLinter' => 'ArcanistLinter',
	'ArcanistMergeConflictLinterTestCase' => 'ArcanistLinterTestCase',
	'ArcanistMessageRevisionHardpointQuery' => 'ArcanistRuntimeHardpointQuery',
	@@ -1544,6 +1561,7 @@
	'ArcanistWorkflowArgument' => 'Phobject',
	'ArcanistWorkflowGitHardpointQuery' => 'ArcanistRuntimeHardpointQuery',
	'ArcanistWorkflowInformation' => 'Phobject',
	+ 'ArcanistWorkflowMercurialHardpointQuery' => 'ArcanistRuntimeHardpointQuery',
	'ArcanistWorkingCopy' => 'Phobject',
	'ArcanistWorkingCopyCommitHardpointQuery' => 'ArcanistRuntimeHardpointQuery',
	'ArcanistWorkingCopyConfigurationSource' => 'ArcanistFilesystemConfigurationSource',
	diff --git a/src/config/arc/ArcanistArcConfigurationEngineExtension.php b/src/config/arc/ArcanistArcConfigurationEngineExtension.php
	--- a/src/config/arc/ArcanistArcConfigurationEngineExtension.php
	+++ b/src/config/arc/ArcanistArcConfigurationEngineExtension.php
	@@ -136,19 +136,15 @@
	array(
	'origin',
	)),
	- id(new ArcanistBoolConfigOption())
	- ->setKey('history.immutable')
	+ id(new ArcanistStringConfigOption())
	+ ->setKey('arc.land.strategy')
	->setSummary(
	pht(
	- 'Configure use of history mutation operations like amends '.
	- 'and rebases.'))
	+ 'Configure a default merge strategy for "arc land".'))
	->setHelp(
	pht(
	- 'If this option is set to "true", Arcanist will treat the '.
	- 'repository history as immutable and will never issue '.
	- 'commands which rewrite repository history (like amends or '.
	- 'rebases). This option defaults to "true" in Mercurial, '.
	- '"false" in Git, and has no effect in Subversion.')),
	+ 'Specifies the default behavior when "arc land" is run with '.
	+ 'no "--strategy" flag.')),
	);
	}

	diff --git a/src/land/ArcanistGitLandEngine.php b/src/land/ArcanistGitLandEngine.php
	deleted file mode 100644
	--- a/src/land/ArcanistGitLandEngine.php
	+++ /dev/null
	@@ -1,913 +0,0 @@
	-<?php
	-
	-final class ArcanistGitLandEngine
	- extends ArcanistLandEngine {
	-
	- private $localRef;
	- private $localCommit;
	- private $sourceCommit;
	- private $mergedRef;
	- private $restoreWhenDestroyed;
	- private $isGitPerforce;
	-
	- private function setIsGitPerforce($is_git_perforce) {
	- $this->isGitPerforce = $is_git_perforce;
	- return $this;
	- }
	-
	- private function getIsGitPerforce() {
	- return $this->isGitPerforce;
	- }
	-
	- public function parseArguments() {
	- $api = $this->getRepositoryAPI();
	-
	- $onto = $this->getEngineOnto();
	- $this->setTargetOnto($onto);
	-
	- $remote = $this->getEngineRemote();
	-
	- $is_pushable = $api->isPushableRemote($remote);
	- $is_perforce = $api->isPerforceRemote($remote);
	-
	- if (!$is_pushable && !$is_perforce) {
	- throw new PhutilArgumentUsageException(
	- pht(
	- 'No pushable remote "%s" exists. Use the "--remote" flag to choose '.
	- 'a valid, pushable remote to land changes onto.',
	- $remote));
	- }
	-
	- if ($is_perforce) {
	- $this->setIsGitPerforce(true);
	- $this->writeWarn(
	- pht('P4 MODE'),
	- pht(
	- 'Operating in Git/Perforce mode after selecting a Perforce '.
	- 'remote.'));
	-
	- if (!$this->getShouldSquash()) {
	- throw new PhutilArgumentUsageException(
	- pht(
	- 'Perforce mode does not support the "merge" land strategy. '.
	- 'Use the "squash" land strategy when landing to a Perforce '.
	- 'remote (you can use "--squash" to select this strategy).'));
	- }
	- }
	-
	- $this->setTargetRemote($remote);
	- }
	-
	- public function execute() {
	- $this->verifySourceAndTargetExist();
	- $this->fetchTarget();
	-
	- $this->printLandingCommits();
	-
	- if ($this->getShouldPreview()) {
	- $this->writeInfo(
	- pht('PREVIEW'),
	- pht('Completed preview of operation.'));
	- return;
	- }
	-
	- $this->saveLocalState();
	-
	- try {
	- $this->identifyRevision();
	- $this->updateWorkingCopy();
	-
	- if ($this->getShouldHold()) {
	- $this->didHoldChanges();
	- } else {
	- $this->pushChange();
	- $this->reconcileLocalState();
	-
	- $api = $this->getRepositoryAPI();
	- $api->execxLocal('submodule update --init --recursive');
	-
	- if ($this->getShouldKeep()) {
	- echo tsprintf(
	- "%s\n",
	- pht('Keeping local branch.'));
	- } else {
	- $this->destroyLocalBranch();
	- }
	-
	- $this->writeOkay(
	- pht('DONE'),
	- pht('Landed changes.'));
	- }
	-
	- $this->restoreWhenDestroyed = false;
	- } catch (Exception $ex) {
	- $this->restoreLocalState();
	- throw $ex;
	- }
	- }
	-
	- public function __destruct() {
	- if ($this->restoreWhenDestroyed) {
	- $this->writeWarn(
	- pht('INTERRUPTED!'),
	- pht('Restoring working copy to its original state.'));
	-
	- $this->restoreLocalState();
	- }
	- }
	-
	- protected function getLandingCommits() {
	- $api = $this->getRepositoryAPI();
	-
	- list($out) = $api->execxLocal(
	- 'log --oneline %s..%s --',
	- $this->getTargetFullRef(),
	- $this->sourceCommit);
	-
	- $out = trim($out);
	-
	- if (!strlen($out)) {
	- return array();
	- } else {
	- return phutil_split_lines($out, false);
	- }
	- }
	-
	- private function identifyRevision() {
	- $api = $this->getRepositoryAPI();
	- $api->execxLocal('checkout %s --', $this->getSourceRef());
	- call_user_func($this->getBuildMessageCallback(), $this);
	- }
	-
	- private function verifySourceAndTargetExist() {
	- $api = $this->getRepositoryAPI();
	-
	- list($err) = $api->execManualLocal(
	- 'rev-parse --verify %s',
	- $this->getTargetFullRef());
	-
	- if ($err) {
	- $this->writeWarn(
	- pht('TARGET'),
	- pht(
	- 'No local ref exists for branch "%s" in remote "%s", attempting '.
	- 'fetch...',
	- $this->getTargetOnto(),
	- $this->getTargetRemote()));
	-
	- $api->execManualLocal(
	- 'fetch %s %s --',
	- $this->getTargetRemote(),
	- $this->getTargetOnto());
	-
	- list($err) = $api->execManualLocal(
	- 'rev-parse --verify %s',
	- $this->getTargetFullRef());
	- if ($err) {
	- throw new Exception(
	- pht(
	- 'Branch "%s" does not exist in remote "%s".',
	- $this->getTargetOnto(),
	- $this->getTargetRemote()));
	- }
	-
	- $this->writeInfo(
	- pht('FETCHED'),
	- pht(
	- 'Fetched branch "%s" from remote "%s".',
	- $this->getTargetOnto(),
	- $this->getTargetRemote()));
	- }
	-
	- list($err, $stdout) = $api->execManualLocal(
	- 'rev-parse --verify %s',
	- $this->getSourceRef());
	-
	- if ($err) {
	- throw new Exception(
	- pht(
	- 'Branch "%s" does not exist in the local working copy.',
	- $this->getSourceRef()));
	- }
	-
	- $this->sourceCommit = trim($stdout);
	- }
	-
	- private function fetchTarget() {
	- $api = $this->getRepositoryAPI();
	-
	- $ref = $this->getTargetFullRef();
	-
	- // NOTE: Although this output isn't hugely useful, we need to passthru
	- // instead of using a subprocess here because `git fetch` may prompt the
	- // user to enter a password if they're fetching over HTTP with basic
	- // authentication. See T10314.
	-
	- if ($this->getIsGitPerforce()) {
	- $this->writeInfo(
	- pht('P4 SYNC'),
	- pht('Synchronizing "%s" from Perforce...', $ref));
	-
	- $sync_ref = sprintf(
	- 'refs/remotes/%s/%s',
	- $this->getTargetRemote(),
	- $this->getTargetOnto());
	-
	- $err = $api->execPassthru(
	- 'p4 sync --silent --branch %R --',
	- $sync_ref);
	-
	- if ($err) {
	- throw new ArcanistUsageException(
	- pht(
	- 'Perforce sync failed! Fix the error and run "arc land" again.'));
	- }
	- } else {
	- $this->writeInfo(
	- pht('FETCH'),
	- pht('Fetching "%s"...', $ref));
	-
	- $err = $api->execPassthru(
	- 'fetch --quiet -- %s %s',
	- $this->getTargetRemote(),
	- $this->getTargetOnto());
	-
	- if ($err) {
	- throw new ArcanistUsageException(
	- pht(
	- 'Fetch failed! Fix the error and run "arc land" again.'));
	- }
	- }
	- }
	-
	- private function updateWorkingCopy() {
	- $api = $this->getRepositoryAPI();
	- $source = $this->sourceCommit;
	-
	- $api->execxLocal(
	- 'checkout %s --',
	- $this->getTargetFullRef());
	-
	- list($original_author, $original_date) = $this->getAuthorAndDate($source);
	-
	- try {
	- if ($this->getShouldSquash()) {
	- // NOTE: We're explicitly specifying "--ff" to override the presence
	- // of "merge.ff" options in user configuration.
	-
	- $api->execxLocal(
	- 'merge --no-stat --no-commit --ff --squash -- %s',
	- $source);
	- } else {
	- $api->execxLocal(
	- 'merge --no-stat --no-commit --no-ff -- %s',
	- $source);
	- }
	- } catch (Exception $ex) {
	- $api->execManualLocal('merge --abort');
	- $api->execManualLocal('reset --hard HEAD --');
	-
	- throw new Exception(
	- pht(
	- 'Local "%s" does not merge cleanly into "%s". Merge or rebase '.
	- 'local changes so they can merge cleanly.',
	- $this->getSourceRef(),
	- $this->getTargetFullRef()));
	- }
	-
	- // TODO: This could probably be cleaner by asking the API a question
	- // about working copy status instead of running a raw diff command. See
	- // discussion in T11435.
	- list($changes) = $api->execxLocal('diff --no-ext-diff HEAD --');
	- $changes = trim($changes);
	- if (!strlen($changes)) {
	- throw new Exception(
	- pht(
	- 'Merging local "%s" into "%s" produces an empty diff. '.
	- 'This usually means these changes have already landed.',
	- $this->getSourceRef(),
	- $this->getTargetFullRef()));
	- }
	-
	- $api->execxLocal(
	- 'commit --author %s --date %s -F %s --',
	- $original_author,
	- $original_date,
	- $this->getCommitMessageFile());
	-
	- $this->getWorkflow()->didCommitMerge();
	-
	- list($stdout) = $api->execxLocal(
	- 'rev-parse --verify %s',
	- 'HEAD');
	- $this->mergedRef = trim($stdout);
	- }
	-
	- private function pushChange() {
	- $api = $this->getRepositoryAPI();
	-
	- if ($this->getIsGitPerforce()) {
	- $this->writeInfo(
	- pht('SUBMITTING'),
	- pht('Submitting changes to "%s".', $this->getTargetFullRef()));
	-
	- $config_argv = array();
	-
	- // Skip the "git p4 submit" interactive editor workflow. We expect
	- // the commit message that "arc land" has built to be satisfactory.
	- $config_argv[] = '-c';
	- $config_argv[] = 'git-p4.skipSubmitEdit=true';
	-
	- // Skip the "git p4 submit" confirmation prompt if the user does not edit
	- // the submit message.
	- $config_argv[] = '-c';
	- $config_argv[] = 'git-p4.skipSubmitEditCheck=true';
	-
	- $flags_argv = array();
	-
	- // Disable implicit "git p4 rebase" as part of submit. We're allowing
	- // the implicit "git p4 sync" to go through since this puts us in a
	- // state which is generally similar to the state after "git push", with
	- // updated remotes.
	-
	- // We could do a manual "git p4 sync" with a more narrow "--branch"
	- // instead, but it's not clear that this is beneficial.
	- $flags_argv[] = '--disable-rebase';
	-
	- // Detect moves and submit them to Perforce as move operations.
	- $flags_argv[] = '-M';
	-
	- // If we run into a conflict, abort the operation. We expect users to
	- // fix conflicts and run "arc land" again.
	- $flags_argv[] = '--conflict=quit';
	-
	- $err = $api->execPassthru(
	- '%LR p4 submit %LR --commit %R --',
	- $config_argv,
	- $flags_argv,
	- $this->mergedRef);
	-
	- if ($err) {
	- throw new ArcanistUsageException(
	- pht(
	- 'Submit failed! Fix the error and run "arc land" again.'));
	- }
	- } else {
	- $this->writeInfo(
	- pht('PUSHING'),
	- pht('Pushing changes to "%s".', $this->getTargetFullRef()));
	-
	- $err = $api->execPassthru(
	- 'push -- %s %s:%s',
	- $this->getTargetRemote(),
	- $this->mergedRef,
	- $this->getTargetOnto());
	-
	- if ($err) {
	- throw new ArcanistUsageException(
	- pht(
	- 'Push failed! Fix the error and run "arc land" again.'));
	- }
	- }
	- }
	-
	- private function reconcileLocalState() {
	- $api = $this->getRepositoryAPI();
	-
	- // Try to put the user into the best final state we can. This is very
	- // complicated because users are incredibly creative and their local
	- // branches may have the same names as branches in the remote but no
	- // relationship to them.
	-
	- if ($this->localRef != $this->getSourceRef()) {
	- // The user ran `arc land X` but was on a different branch, so just put
	- // them back wherever they were before.
	- $this->writeInfo(
	- pht('RESTORE'),
	- pht('Switching back to "%s".', $this->localRef));
	- $this->restoreLocalState();
	- return;
	- }
	-
	- // We're going to try to find a path to the upstream target branch. We
	- // try in two different ways:
	- //
	- // - follow the source branch directly along tracking branches until
	- // we reach the upstream; or
	- // - follow a local branch with the same name as the target branch until
	- // we reach the upstream.
	-
	- // First, get the path from whatever we landed to wherever it goes.
	- $local_branch = $this->getSourceRef();
	-
	- $path = $api->getPathToUpstream($local_branch);
	- if ($path->getLength()) {
	- // We may want to discard the thing we landed from the path, if we're
	- // going to delete it. In this case, we don't want to update it or worry
	- // if it's dirty.
	- if ($this->getSourceRef() == $this->getTargetOnto()) {
	- // In this case, we've done something like land "master" onto itself,
	- // so we do want to update the actual branch. We're going to use the
	- // entire path.
	- } else {
	- // Otherwise, we're going to delete the branch at the end of the
	- // workflow, so throw it away the most-local branch that isn't long
	- // for this world.
	- $path->removeUpstream($local_branch);
	-
	- if (!$path->getLength()) {
	- // The local branch tracked upstream directly; however, it
	- // may not be the only one to do so. If there's a local
	- // branch of the same name that tracks the remote, try
	- // switching to that.
	- $local_branch = $this->getTargetOnto();
	- list($err) = $api->execManualLocal(
	- 'rev-parse --verify %s',
	- $local_branch);
	- if (!$err) {
	- $path = $api->getPathToUpstream($local_branch);
	- }
	- if (!$path->isConnectedToRemote()) {
	- $this->writeInfo(
	- pht('UPDATE'),
	- pht(
	- 'Local branch "%s" directly tracks remote, staying on '.
	- 'detached HEAD.',
	- $local_branch));
	- return;
	- }
	- }
	-
	- $local_branch = head($path->getLocalBranches());
	- }
	- } else {
	- // The source branch has no upstream, so look for a local branch with
	- // the same name as the target branch. This corresponds to the common
	- // case where you have "master" and checkout local branches from it
	- // with "git checkout -b feature", then land onto "master".
	-
	- $local_branch = $this->getTargetOnto();
	-
	- list($err) = $api->execManualLocal(
	- 'rev-parse --verify %s',
	- $local_branch);
	- if ($err) {
	- $this->writeInfo(
	- pht('UPDATE'),
	- pht(
	- 'Local branch "%s" does not exist, staying on detached HEAD.',
	- $local_branch));
	- return;
	- }
	-
	- $path = $api->getPathToUpstream($local_branch);
	- }
	-
	- if ($path->getCycle()) {
	- $this->writeWarn(
	- pht('LOCAL CYCLE'),
	- pht(
	- 'Local branch "%s" tracks an upstream but following it leads to '.
	- 'a local cycle, staying on detached HEAD.',
	- $local_branch));
	- return;
	- }
	-
	- $is_perforce = $this->getIsGitPerforce();
	-
	- if ($is_perforce) {
	- // If we're in Perforce mode, we don't expect to have a meaningful
	- // path to the remote: the "p4" remote is not a real remote, and
	- // "git p4" commands do not configure branch upstreams to provide
	- // a path.
	-
	- // Just pretend the target branch is connected directly to the remote,
	- // since this is effectively the behavior of Perforce and appears to
	- // do the right thing.
	- $cascade_branches = array($local_branch);
	- } else {
	- if (!$path->isConnectedToRemote()) {
	- $this->writeInfo(
	- pht('UPDATE'),
	- pht(
	- 'Local branch "%s" is not connected to a remote, staying on '.
	- 'detached HEAD.',
	- $local_branch));
	- return;
	- }
	-
	- $remote_remote = $path->getRemoteRemoteName();
	- $remote_branch = $path->getRemoteBranchName();
	-
	- $remote_actual = $remote_remote.'/'.$remote_branch;
	- $remote_expect = $this->getTargetFullRef();
	- if ($remote_actual != $remote_expect) {
	- $this->writeInfo(
	- pht('UPDATE'),
	- pht(
	- 'Local branch "%s" is connected to a remote ("%s") other than '.
	- 'the target remote ("%s"), staying on detached HEAD.',
	- $local_branch,
	- $remote_actual,
	- $remote_expect));
	- return;
	- }
	-
	- // If we get this far, we have a sequence of branches which ultimately
	- // connect to the remote. We're going to try to update them all in reverse
	- // order, from most-upstream to most-local.
	-
	- $cascade_branches = $path->getLocalBranches();
	- $cascade_branches = array_reverse($cascade_branches);
	- }
	-
	- // First, check if any of them are ahead of the remote.
	-
	- $ahead_of_remote = array();
	- foreach ($cascade_branches as $cascade_branch) {
	- list($stdout) = $api->execxLocal(
	- 'log %s..%s --',
	- $this->mergedRef,
	- $cascade_branch);
	- $stdout = trim($stdout);
	-
	- if (strlen($stdout)) {
	- $ahead_of_remote[$cascade_branch] = $cascade_branch;
	- }
	- }
	-
	- // We're going to handle the last branch (the thing we ultimately intend
	- // to check out) differently. It's OK if it's ahead of the remote, as long
	- // as we just landed it.
	-
	- $local_ahead = isset($ahead_of_remote[$local_branch]);
	- unset($ahead_of_remote[$local_branch]);
	- $land_self = ($this->getTargetOnto() === $this->getSourceRef());
	-
	- // We aren't going to pull anything if anything upstream from us is ahead
	- // of the remote, or the local is ahead of the remote and we didn't land
	- // it onto itself.
	- $skip_pull = ($ahead_of_remote \|\| ($local_ahead && !$land_self));
	-
	- if ($skip_pull) {
	- $this->writeInfo(
	- pht('UPDATE'),
	- pht(
	- 'Local "%s" is ahead of remote "%s". Checking out "%s" but '.
	- 'not pulling changes.',
	- nonempty(head($ahead_of_remote), $local_branch),
	- $this->getTargetFullRef(),
	- $local_branch));
	-
	- $this->writeInfo(
	- pht('CHECKOUT'),
	- pht(
	- 'Checking out "%s".',
	- $local_branch));
	-
	- $api->execxLocal('checkout %s --', $local_branch);
	-
	- return;
	- }
	-
	- // If nothing upstream from our nearest branch is ahead of the remote,
	- // pull it all.
	-
	- $cascade_targets = array();
	- if (!$ahead_of_remote) {
	- foreach ($cascade_branches as $cascade_branch) {
	- if ($local_ahead && ($local_branch == $cascade_branch)) {
	- continue;
	- }
	- $cascade_targets[] = $cascade_branch;
	- }
	- }
	-
	- if ($is_perforce) {
	- // In Perforce, we've already set the remote to the right state with an
	- // implicit "git p4 sync" during "git p4 submit", and "git pull" isn't a
	- // meaningful operation. We're going to skip this step and jump down to
	- // the "git reset --hard" below to get everything into the right state.
	- } else if ($cascade_targets) {
	- $this->writeInfo(
	- pht('UPDATE'),
	- pht(
	- 'Local "%s" tracks target remote "%s", checking out and '.
	- 'pulling changes.',
	- $local_branch,
	- $this->getTargetFullRef()));
	-
	- foreach ($cascade_targets as $cascade_branch) {
	- $this->writeInfo(
	- pht('PULL'),
	- pht(
	- 'Checking out and pulling "%s".',
	- $cascade_branch));
	-
	- $api->execxLocal('checkout %s --', $cascade_branch);
	- $api->execxLocal(
	- 'pull %s %s --',
	- $this->getTargetRemote(),
	- $cascade_branch);
	- }
	-
	- if (!$local_ahead) {
	- return;
	- }
	- }
	-
	- // In this case, the user did something like land a branch onto itself,
	- // and the branch is tracking the correct remote. We're going to discard
	- // the local state and reset it to the state we just pushed.
	-
	- $this->writeInfo(
	- pht('RESET'),
	- pht(
	- 'Local "%s" landed into remote "%s", resetting local branch to '.
	- 'remote state.',
	- $this->getTargetOnto(),
	- $this->getTargetFullRef()));
	-
	- $api->execxLocal('checkout %s --', $local_branch);
	- $api->execxLocal('reset --hard %s --', $this->getTargetFullRef());
	-
	- return;
	- }
	-
	- private function destroyLocalBranch() {
	- $api = $this->getRepositoryAPI();
	- $source_ref = $this->getSourceRef();
	-
	- if ($source_ref == $this->getTargetOnto()) {
	- // If we landed a branch into a branch with the same name, so don't
	- // destroy it. This prevents us from cleaning up "master" if you're
	- // landing master into itself.
	- return;
	- }
	-
	- // TODO: Maybe this should also recover the proper upstream?
	-
	- // See T10321. If we were not landing a branch, don't try to clean it up.
	- // This happens most often when landing from a detached HEAD.
	- $is_branch = $this->isBranch($source_ref);
	- if (!$is_branch) {
	- echo tsprintf(
	- "%s\n",
	- pht(
	- '(Source "%s" is not a branch, leaving working copy as-is.)',
	- $source_ref));
	- return;
	- }
	-
	- $recovery_command = csprintf(
	- 'git checkout -b %R %R',
	- $source_ref,
	- $this->sourceCommit);
	-
	- echo tsprintf(
	- "%s\n",
	- pht('Cleaning up branch "%s"...', $source_ref));
	-
	- echo tsprintf(
	- "%s\n",
	- pht('(Use `%s` if you want it back.)', $recovery_command));
	-
	- $api->execxLocal('branch -D -- %s', $source_ref);
	- }
	-
	- /**
	- * Save the local working copy state so we can restore it later.
	- */
	- private function saveLocalState() {
	- $api = $this->getRepositoryAPI();
	-
	- $this->localCommit = $api->getWorkingCopyRevision();
	-
	- list($ref) = $api->execxLocal('rev-parse --abbrev-ref HEAD');
	- $ref = trim($ref);
	- if ($ref === 'HEAD') {
	- $ref = $this->localCommit;
	- }
	-
	- $this->localRef = $ref;
	-
	- $this->restoreWhenDestroyed = true;
	- }
	-
	- /**
	- * Restore the working copy to the state it was in before we started
	- * performing writes.
	- */
	- private function restoreLocalState() {
	- $api = $this->getRepositoryAPI();
	-
	- $api->execxLocal('checkout %s --', $this->localRef);
	- $api->execxLocal('reset --hard %s --', $this->localCommit);
	- $api->execxLocal('submodule update --init --recursive');
	-
	- $this->restoreWhenDestroyed = false;
	- }
	-
	- private function getTargetFullRef() {
	- return $this->getTargetRemote().'/'.$this->getTargetOnto();
	- }
	-
	- private function getAuthorAndDate($commit) {
	- $api = $this->getRepositoryAPI();
	-
	- // TODO: This is working around Windows escaping problems, see T8298.
	-
	- list($info) = $api->execxLocal(
	- 'log -n1 --format=%C %s --',
	- '%aD%n%an%n%ae',
	- $commit);
	-
	- $info = trim($info);
	- list($date, $author, $email) = explode("\n", $info, 3);
	-
	- return array(
	- "$author <{$email}>",
	- $date,
	- );
	- }
	-
	- private function didHoldChanges() {
	- if ($this->getIsGitPerforce()) {
	- $this->writeInfo(
	- pht('HOLD'),
	- pht(
	- 'Holding change locally, it has not been submitted.'));
	-
	- $push_command = csprintf(
	- '$ git p4 submit -M --commit %R --',
	- $this->mergedRef);
	- } else {
	- $this->writeInfo(
	- pht('HOLD'),
	- pht(
	- 'Holding change locally, it has not been pushed.'));
	-
	- $push_command = csprintf(
	- '$ git push -- %R %R:%R',
	- $this->getTargetRemote(),
	- $this->mergedRef,
	- $this->getTargetOnto());
	- }
	-
	- $restore_command = csprintf(
	- '$ git checkout %R --',
	- $this->localRef);
	-
	- echo tsprintf(
	- "\n%s\n\n".
	- "%s\n\n".
	- " %s\n\n".
	- "%s\n\n".
	- " %s\n\n".
	- "%s\n",
	- pht(
	- 'This local working copy now contains the merged changes in a '.
	- 'detached state.'),
	- pht('You can push the changes manually with this command:'),
	- $push_command,
	- pht(
	- 'You can go back to how things were before you ran "arc land" with '.
	- 'this command:'),
	- $restore_command,
	- pht(
	- 'Local branches have not been changed, and are still in exactly the '.
	- 'same state as before.'));
	- }
	-
	- private function isBranch($ref) {
	- $api = $this->getRepositoryAPI();
	-
	- list($err) = $api->execManualLocal(
	- 'show-ref --verify --quiet -- %R',
	- 'refs/heads/'.$ref);
	-
	- return !$err;
	- }
	-
	- private function getEngineOnto() {
	- $source_ref = $this->getSourceRef();
	-
	- $onto = $this->getOntoArgument();
	- if ($onto !== null) {
	- $this->writeInfo(
	- pht('TARGET'),
	- pht(
	- 'Landing onto "%s", selected with the "--onto" flag.',
	- $onto));
	- return $onto;
	- }
	-
	- $api = $this->getRepositoryAPI();
	- $path = $api->getPathToUpstream($source_ref);
	-
	- if ($path->getLength()) {
	- $cycle = $path->getCycle();
	- if ($cycle) {
	- $this->writeWarn(
	- pht('LOCAL CYCLE'),
	- pht(
	- 'Local branch tracks an upstream, but following it leads to a '.
	- 'local cycle; ignoring branch upstream.'));
	-
	- echo tsprintf(
	- "\n %s\n\n",
	- implode(' -> ', $cycle));
	-
	- } else {
	- if ($path->isConnectedToRemote()) {
	- $onto = $path->getRemoteBranchName();
	- $this->writeInfo(
	- pht('TARGET'),
	- pht(
	- 'Landing onto "%s", selected by following tracking branches '.
	- 'upstream to the closest remote.',
	- $onto));
	- return $onto;
	- } else {
	- $this->writeInfo(
	- pht('NO PATH TO UPSTREAM'),
	- pht(
	- 'Local branch tracks an upstream, but there is no path '.
	- 'to a remote; ignoring branch upstream.'));
	- }
	- }
	- }
	-
	- $workflow = $this->getWorkflow();
	-
	- $config_key = 'arc.land.onto.default';
	- $onto = $workflow->getConfigFromAnySource($config_key);
	- if ($onto !== null) {
	- $this->writeInfo(
	- pht('TARGET'),
	- pht(
	- 'Landing onto "%s", selected by "%s" configuration.',
	- $onto,
	- $config_key));
	- return $onto;
	- }
	-
	- $onto = 'master';
	- $this->writeInfo(
	- pht('TARGET'),
	- pht(
	- 'Landing onto "%s", the default target under git.',
	- $onto));
	-
	- return $onto;
	- }
	-
	- private function getEngineRemote() {
	- $source_ref = $this->getSourceRef();
	-
	- $remote = $this->getRemoteArgument();
	- if ($remote !== null) {
	- $this->writeInfo(
	- pht('REMOTE'),
	- pht(
	- 'Using remote "%s", selected with the "--remote" flag.',
	- $remote));
	- return $remote;
	- }
	-
	- $api = $this->getRepositoryAPI();
	- $path = $api->getPathToUpstream($source_ref);
	-
	- $remote = $path->getRemoteRemoteName();
	- if ($remote !== null) {
	- $this->writeInfo(
	- pht('REMOTE'),
	- pht(
	- 'Using remote "%s", selected by following tracking branches '.
	- 'upstream to the closest remote.',
	- $remote));
	- return $remote;
	- }
	-
	- $remote = 'p4';
	- if ($api->isPerforceRemote($remote)) {
	- $this->writeInfo(
	- pht('REMOTE'),
	- pht(
	- 'Using Perforce remote "%s". The existence of this remote implies '.
	- 'this working copy was synchronized from a Perforce repository.',
	- $remote));
	- return $remote;
	- }
	-
	- $remote = 'origin';
	- $this->writeInfo(
	- pht('REMOTE'),
	- pht(
	- 'Using remote "%s", the default remote under Git.',
	- $remote));
	-
	- return $remote;
	- }
	-
	-}
	diff --git a/src/land/ArcanistLandCommit.php b/src/land/ArcanistLandCommit.php
	new file mode 100644
	--- /dev/null
	+++ b/src/land/ArcanistLandCommit.php
	@@ -0,0 +1,149 @@
	+<?php
	+
	+final class ArcanistLandCommit
	+ extends Phobject {
	+
	+ private $hash;
	+ private $summary;
	+ private $displaySummary;
	+ private $parents;
	+ private $symbols = array();
	+ private $explicitRevisionRef;
	+ private $revisionRef = false;
	+ private $parentCommits;
	+ private $isHeadCommit;
	+ private $isImplicitCommit;
	+
	+ public function setHash($hash) {
	+ $this->hash = $hash;
	+ return $this;
	+ }
	+
	+ public function getHash() {
	+ return $this->hash;
	+ }
	+
	+ public function setSummary($summary) {
	+ $this->summary = $summary;
	+ return $this;
	+ }
	+
	+ public function getSummary() {
	+ return $this->summary;
	+ }
	+
	+ public function getDisplaySummary() {
	+ if ($this->displaySummary === null) {
	+ $this->displaySummary = id(new PhutilUTF8StringTruncator())
	+ ->setMaximumGlyphs(64)
	+ ->truncateString($this->getSummary());
	+ }
	+ return $this->displaySummary;
	+ }
	+
	+ public function setParents(array $parents) {
	+ $this->parents = $parents;
	+ return $this;
	+ }
	+
	+ public function getParents() {
	+ return $this->parents;
	+ }
	+
	+ public function addSymbol(ArcanistLandSymbol $symbol) {
	+ $this->symbols[] = $symbol;
	+ return $this;
	+ }
	+
	+ public function getSymbols() {
	+ return $this->symbols;
	+ }
	+
	+ public function setExplicitRevisionref(ArcanistRevisionRef $ref) {
	+ $this->explicitRevisionRef = $ref;
	+ return $this;
	+ }
	+
	+ public function getExplicitRevisionref() {
	+ return $this->explicitRevisionRef;
	+ }
	+
	+ public function setParentCommits(array $parent_commits) {
	+ $this->parentCommits = $parent_commits;
	+ return $this;
	+ }
	+
	+ public function getParentCommits() {
	+ return $this->parentCommits;
	+ }
	+
	+ public function setIsHeadCommit($is_head_commit) {
	+ $this->isHeadCommit = $is_head_commit;
	+ return $this;
	+ }
	+
	+ public function getIsHeadCommit() {
	+ return $this->isHeadCommit;
	+ }
	+
	+ public function setIsImplicitCommit($is_implicit_commit) {
	+ $this->isImplicitCommit = $is_implicit_commit;
	+ return $this;
	+ }
	+
	+ public function getIsImplicitCommit() {
	+ return $this->isImplicitCommit;
	+ }
	+
	+ public function getAncestorRevisionPHIDs() {
	+ $phids = array();
	+
	+ foreach ($this->getParentCommits() as $parent_commit) {
	+ $phids += $parent_commit->getAncestorRevisionPHIDs();
	+ }
	+
	+ $revision_ref = $this->getRevisionRef();
	+ if ($revision_ref) {
	+ $phids[$revision_ref->getPHID()] = $revision_ref->getPHID();
	+ }
	+
	+ return $phids;
	+ }
	+
	+ public function getRevisionRef() {
	+ if ($this->revisionRef === false) {
	+ $this->revisionRef = $this->newRevisionRef();
	+ }
	+
	+ return $this->revisionRef;
	+ }
	+
	+ private function newRevisionRef() {
	+ $revision_ref = $this->getExplicitRevisionRef();
	+ if ($revision_ref) {
	+ return $revision_ref;
	+ }
	+
	+ $parent_refs = array();
	+ foreach ($this->getParentCommits() as $parent_commit) {
	+ $parent_ref = $parent_commit->getRevisionRef();
	+ if ($parent_ref) {
	+ $parent_refs[$parent_ref->getPHID()] = $parent_ref;
	+ }
	+ }
	+
	+ if (count($parent_refs) > 1) {
	+ throw new Exception(
	+ pht(
	+ 'Too many distinct parent refs!'));
	+ }
	+
	+ if ($parent_refs) {
	+ return head($parent_refs);
	+ }
	+
	+ return null;
	+ }
	+
	+
	+}
	diff --git a/src/land/ArcanistLandCommitSet.php b/src/land/ArcanistLandCommitSet.php
	new file mode 100644
	--- /dev/null
	+++ b/src/land/ArcanistLandCommitSet.php
	@@ -0,0 +1,52 @@
	+<?php
	+
	+final class ArcanistLandCommitSet
	+ extends Phobject {
	+
	+ private $revisionRef;
	+ private $commits;
	+
	+ public function setRevisionRef(ArcanistRevisionRef $revision_ref) {
	+ $this->revisionRef = $revision_ref;
	+ return $this;
	+ }
	+
	+ public function getRevisionRef() {
	+ return $this->revisionRef;
	+ }
	+
	+ public function setCommits(array $commits) {
	+ assert_instances_of($commits, 'ArcanistLandCommit');
	+ $this->commits = $commits;
	+
	+ $revision_phid = $this->getRevisionRef()->getPHID();
	+ foreach ($commits as $commit) {
	+ $revision_ref = $commit->getExplicitRevisionRef();
	+
	+ if ($revision_ref) {
	+ if ($revision_ref->getPHID() === $revision_phid) {
	+ continue;
	+ }
	+ }
	+
	+ $commit->setIsImplicitCommit(true);
	+ }
	+
	+ return $this;
	+ }
	+
	+ public function getCommits() {
	+ return $this->commits;
	+ }
	+
	+ public function hasImplicitCommits() {
	+ foreach ($this->commits as $commit) {
	+ if ($commit->getIsImplicitCommit()) {
	+ return true;
	+ }
	+ }
	+
	+ return false;
	+ }
	+
	+}
	diff --git a/src/land/ArcanistLandEngine.php b/src/land/ArcanistLandEngine.php
	deleted file mode 100644
	--- a/src/land/ArcanistLandEngine.php
	+++ /dev/null
	@@ -1,182 +0,0 @@
	-<?php
	-
	-abstract class ArcanistLandEngine extends Phobject {
	-
	- private $workflow;
	- private $repositoryAPI;
	- private $targetRemote;
	- private $targetOnto;
	- private $sourceRef;
	- private $commitMessageFile;
	- private $shouldHold;
	- private $shouldKeep;
	- private $shouldSquash;
	- private $shouldDeleteRemote;
	- private $shouldPreview;
	- private $remoteArgument;
	- private $ontoArgument;
	-
	- // TODO: This is really grotesque.
	- private $buildMessageCallback;
	-
	- final public function setWorkflow(ArcanistWorkflow $workflow) {
	- $this->workflow = $workflow;
	- return $this;
	- }
	-
	- final public function getWorkflow() {
	- return $this->workflow;
	- }
	-
	- final public function setRepositoryAPI(
	- ArcanistRepositoryAPI $repository_api) {
	- $this->repositoryAPI = $repository_api;
	- return $this;
	- }
	-
	- final public function getRepositoryAPI() {
	- return $this->repositoryAPI;
	- }
	-
	- final public function setShouldHold($should_hold) {
	- $this->shouldHold = $should_hold;
	- return $this;
	- }
	-
	- final public function getShouldHold() {
	- return $this->shouldHold;
	- }
	-
	- final public function setShouldKeep($should_keep) {
	- $this->shouldKeep = $should_keep;
	- return $this;
	- }
	-
	- final public function getShouldKeep() {
	- return $this->shouldKeep;
	- }
	-
	- final public function setShouldSquash($should_squash) {
	- $this->shouldSquash = $should_squash;
	- return $this;
	- }
	-
	- final public function getShouldSquash() {
	- return $this->shouldSquash;
	- }
	-
	- final public function setShouldPreview($should_preview) {
	- $this->shouldPreview = $should_preview;
	- return $this;
	- }
	-
	- final public function getShouldPreview() {
	- return $this->shouldPreview;
	- }
	-
	- final public function setTargetRemote($target_remote) {
	- $this->targetRemote = $target_remote;
	- return $this;
	- }
	-
	- final public function getTargetRemote() {
	- return $this->targetRemote;
	- }
	-
	- final public function setTargetOnto($target_onto) {
	- $this->targetOnto = $target_onto;
	- return $this;
	- }
	-
	- final public function getTargetOnto() {
	- return $this->targetOnto;
	- }
	-
	- final public function setSourceRef($source_ref) {
	- $this->sourceRef = $source_ref;
	- return $this;
	- }
	-
	- final public function getSourceRef() {
	- return $this->sourceRef;
	- }
	-
	- final public function setBuildMessageCallback($build_message_callback) {
	- $this->buildMessageCallback = $build_message_callback;
	- return $this;
	- }
	-
	- final public function getBuildMessageCallback() {
	- return $this->buildMessageCallback;
	- }
	-
	- final public function setCommitMessageFile($commit_message_file) {
	- $this->commitMessageFile = $commit_message_file;
	- return $this;
	- }
	-
	- final public function getCommitMessageFile() {
	- return $this->commitMessageFile;
	- }
	-
	- final public function setRemoteArgument($remote_argument) {
	- $this->remoteArgument = $remote_argument;
	- return $this;
	- }
	-
	- final public function getRemoteArgument() {
	- return $this->remoteArgument;
	- }
	-
	- final public function setOntoArgument($onto_argument) {
	- $this->ontoArgument = $onto_argument;
	- return $this;
	- }
	-
	- final public function getOntoArgument() {
	- return $this->ontoArgument;
	- }
	-
	- abstract public function parseArguments();
	- abstract public function execute();
	-
	- abstract protected function getLandingCommits();
	-
	- protected function printLandingCommits() {
	- $logs = $this->getLandingCommits();
	-
	- if (!$logs) {
	- throw new ArcanistUsageException(
	- pht(
	- 'There are no commits on "%s" which are not already present on '.
	- 'the target.',
	- $this->getSourceRef()));
	- }
	-
	- $list = id(new PhutilConsoleList())
	- ->setWrap(false)
	- ->addItems($logs);
	-
	- id(new PhutilConsoleBlock())
	- ->addParagraph(
	- pht(
	- 'These %s commit(s) will be landed:',
	- new PhutilNumber(count($logs))))
	- ->addList($list)
	- ->draw();
	- }
	-
	- protected function writeWarn($title, $message) {
	- return $this->getWorkflow()->writeWarn($title, $message);
	- }
	-
	- protected function writeInfo($title, $message) {
	- return $this->getWorkflow()->writeInfo($title, $message);
	- }
	-
	- protected function writeOkay($title, $message) {
	- return $this->getWorkflow()->writeOkay($title, $message);
	- }
	-
	-
	-}
	diff --git a/src/land/ArcanistLandSymbol.php b/src/land/ArcanistLandSymbol.php
	new file mode 100644
	--- /dev/null
	+++ b/src/land/ArcanistLandSymbol.php
	@@ -0,0 +1,27 @@
	+<?php
	+
	+final class ArcanistLandSymbol
	+ extends Phobject {
	+
	+ private $symbol;
	+ private $commit;
	+
	+ public function setSymbol($symbol) {
	+ $this->symbol = $symbol;
	+ return $this;
	+ }
	+
	+ public function getSymbol() {
	+ return $this->symbol;
	+ }
	+
	+ public function setCommit($commit) {
	+ $this->commit = $commit;
	+ return $this;
	+ }
	+
	+ public function getCommit() {
	+ return $this->commit;
	+ }
	+
	+}
	diff --git a/src/land/ArcanistLandTarget.php b/src/land/ArcanistLandTarget.php
	new file mode 100644
	--- /dev/null
	+++ b/src/land/ArcanistLandTarget.php
	@@ -0,0 +1,41 @@
	+<?php
	+
	+final class ArcanistLandTarget
	+ extends Phobject {
	+
	+ private $remote;
	+ private $ref;
	+ private $commit;
	+
	+ public function setRemote($remote) {
	+ $this->remote = $remote;
	+ return $this;
	+ }
	+
	+ public function getRemote() {
	+ return $this->remote;
	+ }
	+
	+ public function setRef($ref) {
	+ $this->ref = $ref;
	+ return $this;
	+ }
	+
	+ public function getRef() {
	+ return $this->ref;
	+ }
	+
	+ public function getLandTargetKey() {
	+ return sprintf('%s/%s', $this->getRemote(), $this->getRef());
	+ }
	+
	+ public function setLandTargetCommit($commit) {
	+ $this->commit = $commit;
	+ return $this;
	+ }
	+
	+ public function getLandTargetCommit() {
	+ return $this->commit;
	+ }
	+
	+}
	diff --git a/src/land/engine/ArcanistGitLandEngine.php b/src/land/engine/ArcanistGitLandEngine.php
	new file mode 100644
	--- /dev/null
	+++ b/src/land/engine/ArcanistGitLandEngine.php
	@@ -0,0 +1,1362 @@
	+<?php
	+
	+final class ArcanistGitLandEngine
	+ extends ArcanistLandEngine {
	+
	+ private $isGitPerforce;
	+ private $landTargetCommitMap = array();
	+ private $deletedBranches = array();
	+
	+ private function setIsGitPerforce($is_git_perforce) {
	+ $this->isGitPerforce = $is_git_perforce;
	+ return $this;
	+ }
	+
	+ private function getIsGitPerforce() {
	+ return $this->isGitPerforce;
	+ }
	+
	+ protected function pruneBranches(array $sets) {
	+ $old_commits = array();
	+ foreach ($sets as $set) {
	+ $hash = last($set->getCommits())->getHash();
	+ $old_commits[] = $hash;
	+ }
	+
	+ $branch_map = $this->getBranchesForCommits(
	+ $old_commits,
	+ $is_contains = false);
	+
	+ $api = $this->getRepositoryAPI();
	+ foreach ($branch_map as $branch_name => $branch_hash) {
	+ $recovery_command = csprintf(
	+ 'git checkout -b %s %s',
	+ $branch_name,
	+ $this->getDisplayHash($branch_hash));
	+
	+ echo tsprintf(
	+ "%s\n",
	+ pht('Cleaning up branch "%s"...', $branch_name));
	+
	+ echo tsprintf(
	+ "%s\n",
	+ pht('(Use `%s` if you want it back.)', $recovery_command));
	+
	+ $api->execxLocal('branch -D -- %s', $branch_name);
	+ $this->deletedBranches[$branch_name] = true;
	+ }
	+ }
	+
	+ private function getBranchesForCommits(array $hashes, $is_contains) {
	+ $api = $this->getRepositoryAPI();
	+
	+ $format = '%(refname) %(objectname)';
	+
	+ $result = array();
	+ foreach ($hashes as $hash) {
	+ if ($is_contains) {
	+ $command = csprintf(
	+ 'for-each-ref --contains %s --format %s --',
	+ $hash,
	+ $format);
	+ } else {
	+ $command = csprintf(
	+ 'for-each-ref --points-at %s --format %s --',
	+ $hash,
	+ $format);
	+ }
	+
	+ list($foreach_lines) = $api->execxLocal('%C', $command);
	+ $foreach_lines = phutil_split_lines($foreach_lines, false);
	+
	+ foreach ($foreach_lines as $line) {
	+ if (!strlen($line)) {
	+ continue;
	+ }
	+
	+ $expect_parts = 2;
	+ $parts = explode(' ', $line, $expect_parts);
	+ if (count($parts) !== $expect_parts) {
	+ throw new Exception(
	+ pht(
	+ 'Failed to explode line "%s".',
	+ $line));
	+ }
	+
	+ $ref_name = $parts[0];
	+ $ref_hash = $parts[1];
	+
	+ $matches = null;
	+ $ok = preg_match('(^refs/heads/(.*)\z)', $ref_name, $matches);
	+ if ($ok === false) {
	+ throw new Exception(
	+ pht(
	+ 'Failed to match against branch pattern "%s".',
	+ $line));
	+ }
	+
	+ if (!$ok) {
	+ continue;
	+ }
	+
	+ $result[$matches[1]] = $ref_hash;
	+ }
	+ }
	+
	+ return $result;
	+ }
	+
	+ protected function cascadeState(ArcanistLandCommitSet $set, $into_commit) {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ // This has no effect when we're executing a merge strategy.
	+ if (!$this->isSquashStrategy()) {
	+ return;
	+ }
	+
	+ $old_commit = last($set->getCommits())->getHash();
	+ $new_commit = $into_commit;
	+
	+ $branch_map = $this->getBranchesForCommits(
	+ array($old_commit),
	+ $is_contains = true);
	+
	+ $log = $this->getLogEngine();
	+ foreach ($branch_map as $branch_name => $branch_head) {
	+ // If this branch just points at the old state, don't bother rebasing
	+ // it. We'll update or delete it later.
	+ if ($branch_head === $old_commit) {
	+ continue;
	+ }
	+
	+ $log->writeStatus(
	+ pht('CASCADE'),
	+ pht(
	+ 'Rebasing "%s" onto landed state...',
	+ $branch_name));
	+
	+ try {
	+ $api->execxLocal(
	+ 'rebase --onto %s -- %s %s',
	+ $new_commit,
	+ $old_commit,
	+ $branch_name);
	+ } catch (CommandException $ex) {
	+ // TODO: If we have a stashed state or are not running in incremental
	+ // mode: abort the rebase, restore the local state, and pop the stash.
	+ // Otherwise, drop the user out here.
	+ throw $ex;
	+ }
	+ }
	+ }
	+
	+ private function fetchTarget(ArcanistLandTarget $target) {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ // NOTE: Although this output isn't hugely useful, we need to passthru
	+ // instead of using a subprocess here because `git fetch` may prompt the
	+ // user to enter a password if they're fetching over HTTP with basic
	+ // authentication. See T10314.
	+
	+ if ($this->getIsGitPerforce()) {
	+ $log->writeStatus(
	+ pht('P4 SYNC'),
	+ pht(
	+ 'Synchronizing "%s" from Perforce...',
	+ $target->getRef()));
	+
	+ $err = $api->execPassthru(
	+ 'p4 sync --silent --branch %s --',
	+ $target->getRemote().'/'.$target->getRef());
	+
	+ if ($err) {
	+ throw new ArcanistUsageException(
	+ pht(
	+ 'Perforce sync failed! Fix the error and run "arc land" again.'));
	+ }
	+
	+ return $this->getLandTargetLocalCommit($target);
	+ }
	+
	+ $exists = $this->getLandTargetLocalExists($target);
	+ if (!$exists) {
	+ $log->writeWarning(
	+ pht('TARGET'),
	+ pht(
	+ 'No local copy of ref "%s" in remote "%s" exists, attempting '.
	+ 'fetch...',
	+ $target->getRef(),
	+ $target->getRemote()));
	+
	+ $this->fetchLandTarget($target, $ignore_failure = true);
	+
	+ $exists = $this->getLandTargetLocalExists($target);
	+ if (!$exists) {
	+ return null;
	+ }
	+
	+ $log->writeStatus(
	+ pht('FETCHED'),
	+ pht(
	+ 'Fetched ref "%s" from remote "%s".',
	+ $target->getRef(),
	+ $target->getRemote()));
	+
	+ return $this->getLandTargetLocalCommit($target);
	+ }
	+
	+ $log->writeStatus(
	+ pht('FETCH'),
	+ pht(
	+ 'Fetching "%s" from remote "%s"...',
	+ $target->getRef(),
	+ $target->getRemote()));
	+
	+ $this->fetchLandTarget($target, $ignore_failure = false);
	+
	+ return $this->getLandTargetLocalCommit($target);
	+ }
	+
	+ private function updateWorkingCopy($into_commit) {
	+ $api = $this->getRepositoryAPI();
	+ if ($into_commit === null) {
	+ throw new Exception('TODO: Author a new empty state.');
	+ } else {
	+ $api->execxLocal('checkout %s --', $into_commit);
	+ }
	+ }
	+
	+ protected function executeMerge(ArcanistLandCommitSet $set, $into_commit) {
	+ $api = $this->getRepositoryAPI();
	+
	+ $this->updateWorkingCopy($into_commit);
	+
	+ $commits = $set->getCommits();
	+ $source_commit = last($commits)->getHash();
	+
	+ // NOTE: See T11435 for some history. See PHI1727 for a case where a user
	+ // modified their working copy while running "arc land". This attempts to
	+ // resist incorrectly detecting simultaneous working copy modifications
	+ // as changes.
	+
	+ list($changes) = $api->execxLocal(
	+ 'diff --no-ext-diff HEAD..%s --',
	+ $source_commit);
	+ $changes = trim($changes);
	+ if (!strlen($changes)) {
	+
	+ // TODO: We could make a more significant effort to identify the
	+ // human-readable symbol which led us to try to land this ref.
	+
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Merging local "%s" into "%s" produces an empty diff. '.
	+ 'This usually means these changes have already landed.',
	+ $this->getDisplayHash($source_commit),
	+ $this->getDisplayHash($into_commit)));
	+ }
	+
	+ list($original_author, $original_date) = $this->getAuthorAndDate(
	+ $source_commit);
	+
	+ try {
	+ if ($this->isSquashStrategy()) {
	+ // NOTE: We're explicitly specifying "--ff" to override the presence
	+ // of "merge.ff" options in user configuration.
	+
	+ $api->execxLocal(
	+ 'merge --no-stat --no-commit --ff --squash -- %s',
	+ $source_commit);
	+ } else {
	+ $api->execxLocal(
	+ 'merge --no-stat --no-commit --no-ff -- %s',
	+ $source_commit);
	+ }
	+ } catch (CommandException $ex) {
	+ $api->execManualLocal('merge --abort');
	+ $api->execManualLocal('reset --hard HEAD --');
	+
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Local "%s" does not merge cleanly into "%s". Merge or rebase '.
	+ 'local changes so they can merge cleanly.',
	+ $source_commit,
	+ $into_commit));
	+ }
	+
	+ $revision_ref = $set->getRevisionRef();
	+ $commit_message = $revision_ref->getCommitMessage();
	+
	+ $future = $api->execFutureLocal(
	+ 'commit --author %s --date %s -F - --',
	+ $original_author,
	+ $original_date);
	+ $future->write($commit_message);
	+ $future->resolvex();
	+
	+ list($stdout) = $api->execxLocal('rev-parse --verify %s', 'HEAD');
	+ $new_cursor = trim($stdout);
	+
	+ if ($into_commit === null) {
	+ if ($this->isSquashStrategy()) {
	+ throw new Exception(
	+ pht('TODO: Rewrite HEAD to have no parents.'));
	+ } else {
	+ throw new Exception(
	+ pht('TODO: Rewrite HEAD to have only source as a parent.'));
	+ }
	+ }
	+
	+ return $new_cursor;
	+ }
	+
	+ protected function pushChange($into_commit) {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ if ($this->getIsGitPerforce()) {
	+
	+ // TODO: Specifying "--onto" more than once is almost certainly an error
	+ // in Perforce.
	+
	+ $log->writeStatus(
	+ pht('SUBMITTING'),
	+ pht(
	+ 'Submitting changes to "%s".',
	+ $this->getOntoRemote()));
	+
	+ $config_argv = array();
	+
	+ // Skip the "git p4 submit" interactive editor workflow. We expect
	+ // the commit message that "arc land" has built to be satisfactory.
	+ $config_argv[] = '-c';
	+ $config_argv[] = 'git-p4.skipSubmitEdit=true';
	+
	+ // Skip the "git p4 submit" confirmation prompt if the user does not edit
	+ // the submit message.
	+ $config_argv[] = '-c';
	+ $config_argv[] = 'git-p4.skipSubmitEditCheck=true';
	+
	+ $flags_argv = array();
	+
	+ // Disable implicit "git p4 rebase" as part of submit. We're allowing
	+ // the implicit "git p4 sync" to go through since this puts us in a
	+ // state which is generally similar to the state after "git push", with
	+ // updated remotes.
	+
	+ // We could do a manual "git p4 sync" with a more narrow "--branch"
	+ // instead, but it's not clear that this is beneficial.
	+ $flags_argv[] = '--disable-rebase';
	+
	+ // Detect moves and submit them to Perforce as move operations.
	+ $flags_argv[] = '-M';
	+
	+ // If we run into a conflict, abort the operation. We expect users to
	+ // fix conflicts and run "arc land" again.
	+ $flags_argv[] = '--conflict=quit';
	+
	+ $err = $api->execPassthru(
	+ '%LR p4 submit %LR --commit %R --',
	+ $config_argv,
	+ $flags_argv,
	+ $into_commit);
	+
	+ if ($err) {
	+ throw new ArcanistUsageException(
	+ pht(
	+ 'Submit failed! Fix the error and run "arc land" again.'));
	+ }
	+
	+ return;
	+ }
	+
	+ $log->writeStatus(
	+ pht('PUSHING'),
	+ pht('Pushing changes to "%s".', $this->getOntoRemote()));
	+
	+ $refspecs = array();
	+ foreach ($this->getOntoRefs() as $onto_ref) {
	+ $refspecs[] = sprintf(
	+ '%s:%s',
	+ $into_commit,
	+ $onto_ref);
	+ }
	+
	+ $err = $api->execPassthru(
	+ 'push -- %s %Ls',
	+ $this->getOntoRemote(),
	+ $refspecs);
	+
	+ if ($err) {
	+ throw new ArcanistUsageException(
	+ pht(
	+ 'Push failed! Fix the error and run "arc land" again.'));
	+ }
	+
	+ // TODO
	+ // if ($this->isGitSvn) {
	+ // $err = phutil_passthru('git svn dcommit');
	+ // $cmd = 'git svn dcommit';
	+
	+ }
	+
	+ protected function reconcileLocalState(
	+ $into_commit,
	+ ArcanistRepositoryLocalState $state) {
	+
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getWorkflow()->getLogEngine();
	+
	+ // Try to put the user into the best final state we can. This is very
	+ // complicated because users are incredibly creative and their local
	+ // branches may, for example, have the same names as branches in the
	+ // remote but no relationship to them.
	+
	+ // First, we're going to try to update these local branches:
	+ //
	+ // - the branch we started on originally; and
	+ // - the local upstreams of the branch we started on originally; and
	+ // - the local branch with the same name as the "into" ref; and
	+ // - the local branch with the same name as the "onto" ref.
	+ //
	+ // These branches may not all exist and may not all be unique.
	+ //
	+ // To be updated, these branches must:
	+ //
	+ // - exist;
	+ // - have not been deleted; and
	+ // - be connected to the remote we pushed into.
	+
	+ $update_branches = array();
	+
	+ $local_ref = $state->getLocalRef();
	+ if ($local_ref !== null) {
	+ $update_branches[] = $local_ref;
	+ }
	+
	+ $local_path = $state->getLocalPath();
	+ if ($local_path) {
	+ foreach ($local_path->getLocalBranches() as $local_branch) {
	+ $update_branches[] = $local_branch;
	+ }
	+ }
	+
	+ if (!$this->getIntoEmpty() && !$this->getIntoLocal()) {
	+ $update_branches[] = $this->getIntoRef();
	+ }
	+
	+ foreach ($this->getOntoRefs() as $onto_ref) {
	+ $update_branches[] = $onto_ref;
	+ }
	+
	+ $update_branches = array_fuse($update_branches);
	+
	+ // Remove any branches we know we deleted.
	+ foreach ($update_branches as $key => $update_branch) {
	+ if (isset($this->deletedBranches[$update_branch])) {
	+ unset($update_branches[$key]);
	+ }
	+ }
	+
	+ // Now, remove any branches which don't actually exist.
	+ foreach ($update_branches as $key => $update_branch) {
	+ list($err) = $api->execManualLocal(
	+ 'rev-parse --verify %s',
	+ $update_branch);
	+ if ($err) {
	+ unset($update_branches[$key]);
	+ }
	+ }
	+
	+ $is_perforce = $this->getIsGitPerforce();
	+ if ($is_perforce) {
	+ // If we're in Perforce mode, we don't expect to have a meaningful
	+ // path to the remote: the "p4" remote is not a real remote, and
	+ // "git p4" commands do not configure branch upstreams to provide
	+ // a path.
	+
	+ // Additionally, we've already set the remote to the right state with an
	+ // implicit "git p4 sync" during "git p4 submit", and "git pull" isn't a
	+ // meaningful operation.
	+
	+ // We're going to skip everything here and just switch to the most
	+ // desirable branch (if we can find one), then reset the state (if that
	+ // operation is safe).
	+
	+ if (!$update_branches) {
	+ $log->writeStatus(
	+ pht('DETACHED HEAD'),
	+ pht(
	+ 'Unable to find any local branches to update, staying on '.
	+ 'detached head.'));
	+ $state->discardLocalState();
	+ return;
	+ }
	+
	+ $dst_branch = head($update_branches);
	+ if (!$this->isAncestorOf($dst_branch, $into_commit)) {
	+ $log->writeStatus(
	+ pht('CHECKOUT'),
	+ pht(
	+ 'Local branch "%s" has unpublished changes, checking it out '.
	+ 'but leaving them in place.',
	+ $dst_branch));
	+ $do_reset = false;
	+ } else {
	+ $log->writeStatus(
	+ pht('UPDATE'),
	+ pht(
	+ 'Switching to local branch "%s".',
	+ $dst_branch));
	+ $do_reset = true;
	+ }
	+
	+ $api->execxLocal('checkout %s --', $dst_branch);
	+
	+ if ($do_reset) {
	+ $api->execxLocal('reset --hard %s --', $into_commit);
	+ }
	+
	+ $state->discardLocalState();
	+ return;
	+ }
	+
	+ $onto_refs = array_fuse($this->getOntoRefs());
	+
	+ $pull_branches = array();
	+ foreach ($update_branches as $update_branch) {
	+ $update_path = $api->getPathToUpstream($update_branch);
	+
	+ // Remove any branches which contain upstream cycles.
	+ if ($update_path->getCycle()) {
	+ $log->writeWarning(
	+ pht('LOCAL CYCLE'),
	+ pht(
	+ 'Local branch "%s" tracks an upstream but following it leads to '.
	+ 'a local cycle, ignoring branch.',
	+ $update_branch));
	+ continue;
	+ }
	+
	+ // Remove any branches not connected to a remote.
	+ if (!$update_path->isConnectedToRemote()) {
	+ continue;
	+ }
	+
	+ // Remove any branches connected to a remote other than the remote
	+ // we actually pushed to.
	+ $remote_name = $update_path->getRemoteRemoteName();
	+ if ($remote_name !== $this->getOntoRemote()) {
	+ continue;
	+ }
	+
	+ // Remove any branches not connected to a branch we pushed to.
	+ $remote_branch = $update_path->getRemoteBranchName();
	+ if (!isset($onto_refs[$remote_branch])) {
	+ continue;
	+ }
	+
	+ // This is the most-desirable path between some local branch and
	+ // an impacted upstream. Select it and continue.
	+ $pull_branches = $update_path->getLocalBranches();
	+ break;
	+ }
	+
	+ // When we update these branches later, we want to start with the branch
	+ // closest to the upstream and work our way down.
	+ $pull_branches = array_reverse($pull_branches);
	+ $pull_branches = array_fuse($pull_branches);
	+
	+ // If we started on a branch and it still exists but is not impacted
	+ // by the changes we made to the remote (i.e., we aren't actually going
	+ // to pull or update it if we continue), just switch back to it now. It's
	+ // okay if this branch is completely unrelated to the changes we just
	+ // landed.
	+
	+ if ($local_ref !== null) {
	+ if (isset($update_branches[$local_ref])) {
	+ if (!isset($pull_branches[$local_ref])) {
	+
	+ $log->writeStatus(
	+ pht('RETURN'),
	+ pht(
	+ 'Returning to original branch "%s" in original state.',
	+ $local_ref));
	+
	+ $state->restoreLocalState();
	+ return;
	+ }
	+ }
	+ }
	+
	+ // Otherwise, if we don't have any path from the upstream to any local
	+ // branch, we don't want to switch to some unrelated branch which happens
	+ // to have the same name as a branch we interacted with. Just stay where
	+ // we ended up.
	+
	+ $dst_branch = null;
	+ if ($pull_branches) {
	+ $dst_branch = null;
	+ foreach ($pull_branches as $pull_branch) {
	+ if (!$this->isAncestorOf($pull_branch, $into_commit)) {
	+
	+ $log->writeStatus(
	+ pht('LOCAL CHANGES'),
	+ pht(
	+ 'Local branch "%s" has unpublished changes, ending updates.',
	+ $pull_branch));
	+
	+ break;
	+ }
	+
	+ $log->writeStatus(
	+ pht('UPDATE'),
	+ pht(
	+ 'Updating local branch "%s"...',
	+ $pull_branch));
	+
	+ $api->execxLocal(
	+ 'branch -f %s %s --',
	+ $pull_branch,
	+ $into_commit);
	+
	+ $dst_branch = $pull_branch;
	+ }
	+ }
	+
	+ if ($dst_branch) {
	+ $log->writeStatus(
	+ pht('CHECKOUT'),
	+ pht(
	+ 'Checking out "%s".',
	+ $dst_branch));
	+
	+ $api->execxLocal('checkout %s --', $dst_branch);
	+ } else {
	+ $log->writeStatus(
	+ pht('DETACHED HEAD'),
	+ pht(
	+ 'Unable to find any local branches to update, staying on '.
	+ 'detached head.'));
	+ }
	+
	+ $state->discardLocalState();
	+ }
	+
	+ private function isAncestorOf($branch, $commit) {
	+ $api = $this->getRepositoryAPI();
	+
	+ list($stdout) = $api->execxLocal(
	+ 'merge-base %s %s',
	+ $branch,
	+ $commit);
	+ $merge_base = trim($stdout);
	+
	+ list($stdout) = $api->execxLocal(
	+ 'rev-parse --verify %s',
	+ $branch);
	+ $branch_hash = trim($stdout);
	+
	+ return ($merge_base === $branch_hash);
	+ }
	+
	+ private function getAuthorAndDate($commit) {
	+ $api = $this->getRepositoryAPI();
	+
	+ list($info) = $api->execxLocal(
	+ 'log -n1 --format=%s %s --',
	+ '%aD%n%an%n%ae',
	+ $commit);
	+
	+ $info = trim($info);
	+ list($date, $author, $email) = explode("\n", $info, 3);
	+
	+ return array(
	+ "$author <{$email}>",
	+ $date,
	+ );
	+ }
	+
	+ private function didHoldChanges() {
	+ $log = $this->getLogEngine();
	+
	+ if ($this->getIsGitPerforce()) {
	+ $this->writeInfo(
	+ pht('HOLD'),
	+ pht(
	+ 'Holding change locally, it has not been submitted.'));
	+
	+ $push_command = csprintf(
	+ '$ git p4 submit -M --commit %R --',
	+ $this->mergedRef);
	+ } else {
	+ $log->writeStatus(
	+ pht('HOLD'),
	+ pht(
	+ 'Holding change locally, it has not been pushed.'));
	+
	+ $push_command = csprintf(
	+ '$ git push -- %R %R:%R',
	+ $this->getTargetRemote(),
	+ $this->mergedRef,
	+ $this->getTargetOnto());
	+ }
	+
	+ $restore_command = csprintf(
	+ '$ git checkout %R --',
	+ $this->localRef);
	+
	+ echo tsprintf(
	+ "\n%s\n\n".
	+ "%s\n\n".
	+ " %s\n\n".
	+ "%s\n\n".
	+ " %s\n\n".
	+ "%s\n",
	+ pht(
	+ 'This local working copy now contains the merged changes in a '.
	+ 'detached state.'),
	+ pht('You can push the changes manually with this command:'),
	+ $push_command,
	+ pht(
	+ 'You can go back to how things were before you ran "arc land" with '.
	+ 'this command:'),
	+ $restore_command,
	+ pht(
	+ 'Local branches have not been changed, and are still in exactly the '.
	+ 'same state as before.'));
	+ }
	+
	+ protected function resolveSymbols(array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $api = $this->getRepositoryAPI();
	+
	+ foreach ($symbols as $symbol) {
	+ $raw_symbol = $symbol->getSymbol();
	+
	+ list($err, $stdout) = $api->execManualLocal(
	+ 'rev-parse --verify %s',
	+ $raw_symbol);
	+
	+ if ($err) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Branch "%s" does not exist in the local working copy.',
	+ $raw_symbol));
	+ }
	+
	+ $commit = trim($stdout);
	+ $symbol->setCommit($commit);
	+ }
	+ }
	+
	+ protected function confirmOntoRefs(array $onto_refs) {
	+ foreach ($onto_refs as $onto_ref) {
	+ if (!strlen($onto_ref)) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Selected "onto" ref "%s" is invalid: the empty string is not '.
	+ 'a valid ref.',
	+ $onto_ref));
	+ }
	+ }
	+ }
	+
	+ protected function selectOntoRefs(array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $log = $this->getLogEngine();
	+
	+ $onto = $this->getOntoArguments();
	+ if ($onto) {
	+
	+ $log->writeStatus(
	+ pht('ONTO TARGET'),
	+ pht(
	+ 'Refs were selected with the "--onto" flag: %s.',
	+ implode(', ', $onto)));
	+
	+ return $onto;
	+ }
	+
	+ $onto = $this->getOntoFromConfiguration();
	+ if ($onto) {
	+ $onto_key = $this->getOntoConfigurationKey();
	+
	+ $log->writeStatus(
	+ pht('ONTO TARGET'),
	+ pht(
	+ 'Refs were selected by reading "%s" configuration: %s.',
	+ $onto_key,
	+ implode(', ', $onto)));
	+
	+ return $onto;
	+ }
	+
	+ $api = $this->getRepositoryAPI();
	+
	+ $remote_onto = array();
	+ foreach ($symbols as $symbol) {
	+ $raw_symbol = $symbol->getSymbol();
	+ $path = $api->getPathToUpstream($raw_symbol);
	+
	+ if (!$path->getLength()) {
	+ continue;
	+ }
	+
	+ $cycle = $path->getCycle();
	+ if ($cycle) {
	+ $log->writeWarning(
	+ pht('LOCAL CYCLE'),
	+ pht(
	+ 'Local branch "%s" tracks an upstream, but following it leads '.
	+ 'to a local cycle; ignoring branch upstream.',
	+ $raw_symbol));
	+
	+ $log->writeWarning(
	+ pht('LOCAL CYCLE'),
	+ implode(' -> ', $cycle));
	+
	+ continue;
	+ }
	+
	+ if (!$path->isConnectedToRemote()) {
	+ $log->writeWarning(
	+ pht('NO PATH TO REMOTE'),
	+ pht(
	+ 'Local branch "%s" tracks an upstream, but there is no path '.
	+ 'to a remote; ignoring branch upstream.',
	+ $raw_symbol));
	+
	+ continue;
	+ }
	+
	+ $onto = $path->getRemoteBranchName();
	+
	+ $remote_onto[$onto] = $onto;
	+ }
	+
	+ if (count($remote_onto) > 1) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'The branches you are landing are connected to multiple different '.
	+ 'remote branches via Git branch upstreams. Use "--onto" to select '.
	+ 'the refs you want to push to.'));
	+ }
	+
	+ if ($remote_onto) {
	+ $remote_onto = array_values($remote_onto);
	+
	+ $log->writeStatus(
	+ pht('ONTO TARGET'),
	+ pht(
	+ 'Landing onto target "%s", selected by following tracking branches '.
	+ 'upstream to the closest remote branch.',
	+ head($remote_onto)));
	+
	+ return $remote_onto;
	+ }
	+
	+ $default_onto = 'master';
	+
	+ $log->writeStatus(
	+ pht('ONTO TARGET'),
	+ pht(
	+ 'Landing onto target "%s", the default target under Git.',
	+ $default_onto));
	+
	+ return array($default_onto);
	+ }
	+
	+ protected function selectOntoRemote(array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $remote = $this->newOntoRemote($symbols);
	+
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+ $is_pushable = $api->isPushableRemote($remote);
	+ $is_perforce = $api->isPerforceRemote($remote);
	+
	+ if (!$is_pushable && !$is_perforce) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'No pushable remote "%s" exists. Use the "--onto-remote" flag to '.
	+ 'choose a valid, pushable remote to land changes onto.',
	+ $remote));
	+ }
	+
	+ if ($is_perforce) {
	+ $this->setIsGitPerforce(true);
	+
	+ $log->writeWarning(
	+ pht('P4 MODE'),
	+ pht(
	+ 'Operating in Git/Perforce mode after selecting a Perforce '.
	+ 'remote.'));
	+
	+ if (!$this->isSquashStrategy()) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Perforce mode does not support the "merge" land strategy. '.
	+ 'Use the "squash" land strategy when landing to a Perforce '.
	+ 'remote (you can use "--squash" to select this strategy).'));
	+ }
	+ }
	+
	+ return $remote;
	+ }
	+
	+ private function newOntoRemote(array $onto_symbols) {
	+ assert_instances_of($onto_symbols, 'ArcanistLandSymbol');
	+ $log = $this->getLogEngine();
	+
	+ $remote = $this->getOntoRemoteArgument();
	+ if ($remote !== null) {
	+
	+ $log->writeStatus(
	+ pht('ONTO REMOTE'),
	+ pht(
	+ 'Remote "%s" was selected with the "--onto-remote" flag.',
	+ $remote));
	+
	+ return $remote;
	+ }
	+
	+ $remote = $this->getOntoRemoteFromConfiguration();
	+ if ($remote !== null) {
	+ $remote_key = $this->getOntoRemoteConfigurationKey();
	+
	+ $log->writeStatus(
	+ pht('ONTO REMOTE'),
	+ pht(
	+ 'Remote "%s" was selected by reading "%s" configuration.',
	+ $remote,
	+ $remote_key));
	+
	+ return $remote;
	+ }
	+
	+ $api = $this->getRepositoryAPI();
	+
	+ $upstream_remotes = array();
	+ foreach ($onto_symbols as $onto_symbol) {
	+ $path = $api->getPathToUpstream($onto_symbol->getSymbol());
	+
	+ $remote = $path->getRemoteRemoteName();
	+ if ($remote !== null) {
	+ $upstream_remotes[$remote][] = $onto_symbol;
	+ }
	+ }
	+
	+ if (count($upstream_remotes) > 1) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'The "onto" refs you have selected are connected to multiple '.
	+ 'different remotes via Git branch upstreams. Use "--onto-remote" '.
	+ 'to select a single remote.'));
	+ }
	+
	+ if ($upstream_remotes) {
	+ $upstream_remote = head_key($upstream_remotes);
	+
	+ $log->writeStatus(
	+ pht('ONTO REMOTE'),
	+ pht(
	+ 'Remote "%s" was selected by following tracking branches '.
	+ 'upstream to the closest remote.',
	+ $remote));
	+
	+ return $upstream_remote;
	+ }
	+
	+ $perforce_remote = 'p4';
	+ if ($api->isPerforceRemote($remote)) {
	+
	+ $log->writeStatus(
	+ pht('ONTO REMOTE'),
	+ pht(
	+ 'Peforce remote "%s" was selected because the existence of '.
	+ 'this remote implies this working copy was synchronized '.
	+ 'from a Perforce repository.',
	+ $remote));
	+
	+ return $remote;
	+ }
	+
	+ $default_remote = 'origin';
	+
	+ $log->writeStatus(
	+ pht('ONTO REMOTE'),
	+ pht(
	+ 'Landing onto remote "%s", the default remote under Git.',
	+ $default_remote));
	+
	+ return $default_remote;
	+ }
	+
	+ protected function selectIntoRemote() {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ if ($this->getIntoEmptyArgument()) {
	+ $this->setIntoEmpty(true);
	+
	+ $log->writeStatus(
	+ pht('INTO REMOTE'),
	+ pht(
	+ 'Will merge into empty state, selected with the "--into-empty" '.
	+ 'flag.'));
	+
	+ return;
	+ }
	+
	+ if ($this->getIntoLocalArgument()) {
	+ $this->setIntoLocal(true);
	+
	+ $log->writeStatus(
	+ pht('INTO REMOTE'),
	+ pht(
	+ 'Will merge into local state, selected with the "--into-local" '.
	+ 'flag.'));
	+
	+ return;
	+ }
	+
	+ $into = $this->getIntoRemoteArgument();
	+ if ($into !== null) {
	+
	+ // TODO: We could allow users to pass a URI argument instead, but
	+ // this also requires some updates to the fetch logic elsewhere.
	+
	+ if (!$api->isFetchableRemote($into)) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Remote "%s", specified with "--into", is not a valid fetchable '.
	+ 'remote.',
	+ $into));
	+ }
	+
	+ $this->setIntoRemote($into);
	+
	+ $log->writeStatus(
	+ pht('INTO REMOTE'),
	+ pht(
	+ 'Will merge into remote "%s", selected with the "--into" flag.',
	+ $into));
	+
	+ return;
	+ }
	+
	+ $onto = $this->getOntoRemote();
	+ $this->setIntoRemote($onto);
	+
	+ $log->writeStatus(
	+ pht('INTO REMOTE'),
	+ pht(
	+ 'Will merge into remote "%s" by default, because this is the remote '.
	+ 'the change is landing onto.',
	+ $onto));
	+ }
	+
	+ protected function selectIntoRef() {
	+ $log = $this->getLogEngine();
	+
	+ if ($this->getIntoEmptyArgument()) {
	+ $log->writeStatus(
	+ pht('INTO TARGET'),
	+ pht(
	+ 'Will merge into empty state, selected with the "--into-empty" '.
	+ 'flag.'));
	+
	+ return;
	+ }
	+
	+ $into = $this->getIntoArgument();
	+ if ($into !== null) {
	+ $this->setIntoRef($into);
	+
	+ $log->writeStatus(
	+ pht('INTO TARGET'),
	+ pht(
	+ 'Will merge into target "%s", selected with the "--into" flag.',
	+ $into));
	+
	+ return;
	+ }
	+
	+ $ontos = $this->getOntoRefs();
	+ $onto = head($ontos);
	+
	+ $this->setIntoRef($onto);
	+ if (count($ontos) > 1) {
	+ $log->writeStatus(
	+ pht('INTO TARGET'),
	+ pht(
	+ 'Will merge into target "%s" by default, because this is the first '.
	+ '"onto" target.',
	+ $onto));
	+ } else {
	+ $log->writeStatus(
	+ pht('INTO TARGET'),
	+ pht(
	+ 'Will merge into target "%s" by default, because this is the "onto" '.
	+ 'target.',
	+ $onto));
	+ }
	+ }
	+
	+ protected function selectIntoCommit() {
	+ // Make sure that our "into" target is valid.
	+ $log = $this->getLogEngine();
	+
	+ if ($this->getIntoEmpty()) {
	+ // If we're running under "--into-empty", we don't have to do anything.
	+
	+ $log->writeStatus(
	+ pht('INTO COMMIT'),
	+ pht('Preparing merge into the empty state.'));
	+
	+ return null;
	+ }
	+
	+ if ($this->getIntoLocal()) {
	+ // If we're running under "--into-local", just make sure that the
	+ // target identifies some actual commit.
	+ $api = $this->getRepositoryAPI();
	+ $local_ref = $this->getIntoRef();
	+
	+ list($err, $stdout) = $api->execManualLocal(
	+ 'rev-parse --verify %s',
	+ $local_ref);
	+
	+ if ($err) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Local ref "%s" does not exist.',
	+ $local_ref));
	+ }
	+
	+ $into_commit = trim($stdout);
	+
	+ $log->writeStatus(
	+ pht('INTO COMMIT'),
	+ pht(
	+ 'Preparing merge into local target "%s", at commit "%s".',
	+ $local_ref,
	+ $this->getDisplayHash($into_commit)));
	+
	+ return $into_commit;
	+ }
	+
	+ $target = id(new ArcanistLandTarget())
	+ ->setRemote($this->getIntoRemote())
	+ ->setRef($this->getIntoRef());
	+
	+ $commit = $this->fetchTarget($target);
	+ if ($commit !== null) {
	+ $log->writeStatus(
	+ pht('INTO COMMIT'),
	+ pht(
	+ 'Preparing merge into "%s" from remote "%s", at commit "%s".',
	+ $target->getRef(),
	+ $target->getRemote(),
	+ $this->getDisplayHash($commit)));
	+ return $commit;
	+ }
	+
	+ // If we have no valid target and the user passed "--into" explicitly,
	+ // treat this as an error. For example, "arc land --into Q --onto Q",
	+ // where "Q" does not exist, is an error.
	+ if ($this->getIntoArgument()) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Ref "%s" does not exist in remote "%s".',
	+ $target->getRef(),
	+ $target->getRemote()));
	+ }
	+
	+ // Otherwise, treat this as implying "--into-empty". For example,
	+ // "arc land --onto Q", where "Q" does not exist, is equivalent to
	+ // "arc land --into-empty --onto Q".
	+ $this->setIntoEmpty(true);
	+
	+ $log->writeStatus(
	+ pht('INTO COMMIT'),
	+ pht(
	+ 'Preparing merge into the empty state to create target "%s" '.
	+ 'in remote "%s".',
	+ $target->getRef(),
	+ $target->getRemote()));
	+
	+ return null;
	+ }
	+
	+ private function getLandTargetLocalCommit(ArcanistLandTarget $target) {
	+ $commit = $this->resolveLandTargetLocalCommit($target);
	+
	+ if ($commit === null) {
	+ throw new Exception(
	+ pht(
	+ 'No ref "%s" exists in remote "%s".',
	+ $target->getRef(),
	+ $target->getRemote()));
	+ }
	+
	+ return $commit;
	+ }
	+
	+ private function getLandTargetLocalExists(ArcanistLandTarget $target) {
	+ $commit = $this->resolveLandTargetLocalCommit($target);
	+ return ($commit !== null);
	+ }
	+
	+ private function resolveLandTargetLocalCommit(ArcanistLandTarget $target) {
	+ $target_key = $target->getLandTargetKey();
	+
	+ if (!array_key_exists($target_key, $this->landTargetCommitMap)) {
	+ $full_ref = sprintf(
	+ 'refs/remotes/%s/%s',
	+ $target->getRemote(),
	+ $target->getRef());
	+
	+ $api = $this->getRepositoryAPI();
	+
	+ list($err, $stdout) = $api->execManualLocal(
	+ 'rev-parse --verify %s',
	+ $full_ref);
	+
	+ if ($err) {
	+ $result = null;
	+ } else {
	+ $result = trim($stdout);
	+ }
	+
	+ $this->landTargetCommitMap[$target_key] = $result;
	+ }
	+
	+ return $this->landTargetCommitMap[$target_key];
	+ }
	+
	+ private function fetchLandTarget(
	+ ArcanistLandTarget $target,
	+ $ignore_failure = false) {
	+ $api = $this->getRepositoryAPI();
	+
	+ // TODO: Format this fetch nicely as a workflow command.
	+
	+ $err = $api->execPassthru(
	+ 'fetch --no-tags --quiet -- %s %s',
	+ $target->getRemote(),
	+ $target->getRef());
	+ if ($err && !$ignore_failure) {
	+ throw new ArcanistUsageException(
	+ pht(
	+ 'Fetch of "%s" from remote "%s" failed! Fix the error and '.
	+ 'run "arc land" again.',
	+ $target->getRef(),
	+ $target->getRemote()));
	+ }
	+
	+ // TODO: If the remote is a bare URI, we could read ".git/FETCH_HEAD"
	+ // here and write the commit into the map. For now, settle for clearing
	+ // the cache.
	+
	+ // We could also fetch into some named "refs/arc-land-temporary" named
	+ // ref, then read that.
	+
	+ if (!$err) {
	+ $target_key = $target->getLandTargetKey();
	+ unset($this->landTargetCommitMap[$target_key]);
	+ }
	+ }
	+
	+ protected function selectCommits($into_commit, array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $api = $this->getRepositoryAPI();
	+
	+ $commit_map = array();
	+ foreach ($symbols as $symbol) {
	+ $symbol_commit = $symbol->getCommit();
	+ $format = '%H%x00%P%x00%s%x00';
	+
	+ if ($into_commit === null) {
	+ list($commits) = $api->execxLocal(
	+ 'log %s --format=%s',
	+ $symbol_commit,
	+ $format);
	+ } else {
	+ list($commits) = $api->execxLocal(
	+ 'log %s --not %s --format=%s',
	+ $symbol_commit,
	+ $into_commit,
	+ $format);
	+ }
	+
	+ $commits = phutil_split_lines($commits, false);
	+ foreach ($commits as $line) {
	+ if (!strlen($line)) {
	+ continue;
	+ }
	+
	+ $parts = explode("\0", $line, 4);
	+ if (count($parts) < 3) {
	+ throw new Exception(
	+ pht(
	+ 'Unexpected output from "git log ...": %s',
	+ $line));
	+ }
	+
	+ $hash = $parts[0];
	+ if (!isset($commit_map[$hash])) {
	+ $parents = $parts[1];
	+ $parents = trim($parents);
	+ if (strlen($parents)) {
	+ $parents = explode(' ', $parents);
	+ } else {
	+ $parents = array();
	+ }
	+
	+ $summary = $parts[2];
	+
	+ $commit_map[$hash] = id(new ArcanistLandCommit())
	+ ->setHash($hash)
	+ ->setParents($parents)
	+ ->setSummary($summary);
	+ }
	+
	+ $commit = $commit_map[$hash];
	+ $commit->addSymbol($symbol);
	+ }
	+ }
	+
	+ return $this->confirmCommits($into_commit, $symbols, $commit_map);
	+ }
	+
	+ protected function getDefaultSymbols() {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ $branch = $api->getBranchName();
	+ if ($branch === null) {
	+ $log->writeStatus(
	+ pht('SOURCE'),
	+ pht(
	+ 'Landing the current branch, "%s".',
	+ $branch));
	+
	+ return array($branch);
	+ }
	+
	+ $commit = $api->getCurrentCommitRef();
	+
	+ $log->writeStatus(
	+ pht('SOURCE'),
	+ pht(
	+ 'Landing the current HEAD, "%s".',
	+ $commit->getCommitHash()));
	+
	+ return array($branch);
	+ }
	+
	+}
	diff --git a/src/land/engine/ArcanistLandEngine.php b/src/land/engine/ArcanistLandEngine.php
	new file mode 100644
	--- /dev/null
	+++ b/src/land/engine/ArcanistLandEngine.php
	@@ -0,0 +1,1430 @@
	+<?php
	+
	+abstract class ArcanistLandEngine extends Phobject {
	+
	+ private $workflow;
	+ private $viewer;
	+ private $logEngine;
	+ private $repositoryAPI;
	+
	+ private $sourceRefs;
	+ private $shouldHold;
	+ private $shouldKeep;
	+ private $shouldPreview;
	+ private $isIncremental;
	+ private $ontoRemoteArgument;
	+ private $ontoArguments;
	+ private $intoEmptyArgument;
	+ private $intoLocalArgument;
	+ private $intoRemoteArgument;
	+ private $intoArgument;
	+ private $strategyArgument;
	+ private $strategy;
	+
	+ private $revisionSymbol;
	+ private $revisionSymbolRef;
	+
	+ private $ontoRemote;
	+ private $ontoRefs;
	+ private $intoRemote;
	+ private $intoRef;
	+ private $intoEmpty;
	+ private $intoLocal;
	+
	+ final public function setViewer($viewer) {
	+ $this->viewer = $viewer;
	+ return $this;
	+ }
	+
	+ final public function getViewer() {
	+ return $this->viewer;
	+ }
	+
	+ final public function setOntoRemote($onto_remote) {
	+ $this->ontoRemote = $onto_remote;
	+ return $this;
	+ }
	+
	+ final public function getOntoRemote() {
	+ return $this->ontoRemote;
	+ }
	+
	+ final public function setOntoRefs($onto_refs) {
	+ $this->ontoRefs = $onto_refs;
	+ return $this;
	+ }
	+
	+ final public function getOntoRefs() {
	+ return $this->ontoRefs;
	+ }
	+
	+ final public function setIntoRemote($into_remote) {
	+ $this->intoRemote = $into_remote;
	+ return $this;
	+ }
	+
	+ final public function getIntoRemote() {
	+ return $this->intoRemote;
	+ }
	+
	+ final public function setIntoRef($into_ref) {
	+ $this->intoRef = $into_ref;
	+ return $this;
	+ }
	+
	+ final public function getIntoRef() {
	+ return $this->intoRef;
	+ }
	+
	+ final public function setIntoEmpty($into_empty) {
	+ $this->intoEmpty = $into_empty;
	+ return $this;
	+ }
	+
	+ final public function getIntoEmpty() {
	+ return $this->intoEmpty;
	+ }
	+
	+ final public function setIntoLocal($into_local) {
	+ $this->intoLocal = $into_local;
	+ return $this;
	+ }
	+
	+ final public function getIntoLocal() {
	+ return $this->intoLocal;
	+ }
	+
	+ final public function setWorkflow($workflow) {
	+ $this->workflow = $workflow;
	+ return $this;
	+ }
	+
	+ final public function getWorkflow() {
	+ return $this->workflow;
	+ }
	+
	+ final public function setRepositoryAPI(
	+ ArcanistRepositoryAPI $repository_api) {
	+ $this->repositoryAPI = $repository_api;
	+ return $this;
	+ }
	+
	+ final public function getRepositoryAPI() {
	+ return $this->repositoryAPI;
	+ }
	+
	+ final public function setLogEngine(ArcanistLogEngine $log_engine) {
	+ $this->logEngine = $log_engine;
	+ return $this;
	+ }
	+
	+ final public function getLogEngine() {
	+ return $this->logEngine;
	+ }
	+
	+ final public function setShouldHold($should_hold) {
	+ $this->shouldHold = $should_hold;
	+ return $this;
	+ }
	+
	+ final public function getShouldHold() {
	+ return $this->shouldHold;
	+ }
	+
	+ final public function setShouldKeep($should_keep) {
	+ $this->shouldKeep = $should_keep;
	+ return $this;
	+ }
	+
	+ final public function getShouldKeep() {
	+ return $this->shouldKeep;
	+ }
	+
	+ final public function setStrategy($strategy) {
	+ $this->strategy = $strategy;
	+ return $this;
	+ }
	+
	+ final public function getStrategy() {
	+ return $this->strategy;
	+ }
	+
	+ final public function setRevisionSymbol($revision_symbol) {
	+ $this->revisionSymbol = $revision_symbol;
	+ return $this;
	+ }
	+
	+ final public function getRevisionSymbol() {
	+ return $this->revisionSymbol;
	+ }
	+
	+ final public function setRevisionSymbolRef(
	+ ArcanistRevisionSymbolRef $revision_ref) {
	+ $this->revisionSymbolRef = $revision_ref;
	+ return $this;
	+ }
	+
	+ final public function getRevisionSymbolRef() {
	+ return $this->revisionSymbolRef;
	+ }
	+
	+ final public function setShouldPreview($should_preview) {
	+ $this->shouldPreview = $should_preview;
	+ return $this;
	+ }
	+
	+ final public function getShouldPreview() {
	+ return $this->shouldPreview;
	+ }
	+
	+ final public function setSourceRefs(array $source_refs) {
	+ $this->sourceRefs = $source_refs;
	+ return $this;
	+ }
	+
	+ final public function getSourceRefs() {
	+ return $this->sourceRefs;
	+ }
	+
	+ final public function setOntoRemoteArgument($remote_argument) {
	+ $this->ontoRemoteArgument = $remote_argument;
	+ return $this;
	+ }
	+
	+ final public function getOntoRemoteArgument() {
	+ return $this->ontoRemoteArgument;
	+ }
	+
	+ final public function setOntoArguments(array $onto_arguments) {
	+ $this->ontoArguments = $onto_arguments;
	+ return $this;
	+ }
	+
	+ final public function getOntoArguments() {
	+ return $this->ontoArguments;
	+ }
	+
	+ final public function setIsIncremental($is_incremental) {
	+ $this->isIncremental = $is_incremental;
	+ return $this;
	+ }
	+
	+ final public function getIsIncremental() {
	+ return $this->isIncremental;
	+ }
	+
	+ final public function setIntoEmptyArgument($into_empty_argument) {
	+ $this->intoEmptyArgument = $into_empty_argument;
	+ return $this;
	+ }
	+
	+ final public function getIntoEmptyArgument() {
	+ return $this->intoEmptyArgument;
	+ }
	+
	+ final public function setIntoLocalArgument($into_local_argument) {
	+ $this->intoLocalArgument = $into_local_argument;
	+ return $this;
	+ }
	+
	+ final public function getIntoLocalArgument() {
	+ return $this->intoLocalArgument;
	+ }
	+
	+ final public function setIntoRemoteArgument($into_remote_argument) {
	+ $this->intoRemoteArgument = $into_remote_argument;
	+ return $this;
	+ }
	+
	+ final public function getIntoRemoteArgument() {
	+ return $this->intoRemoteArgument;
	+ }
	+
	+ final public function setIntoArgument($into_argument) {
	+ $this->intoArgument = $into_argument;
	+ return $this;
	+ }
	+
	+ final public function getIntoArgument() {
	+ return $this->intoArgument;
	+ }
	+
	+ final protected function getOntoFromConfiguration() {
	+ $config_key = $this->getOntoConfigurationKey();
	+ return $this->getWorkflow()->getConfig($config_key);
	+ }
	+
	+ final protected function getOntoConfigurationKey() {
	+ return 'arc.land.onto';
	+ }
	+
	+ final protected function getOntoRemoteFromConfiguration() {
	+ $config_key = $this->getOntoRemoteConfigurationKey();
	+ return $this->getWorkflow()->getConfig($config_key);
	+ }
	+
	+ final protected function getOntoRemoteConfigurationKey() {
	+ return 'arc.land.onto-remote';
	+ }
	+
	+ final protected function confirmRevisions(array $sets) {
	+ assert_instances_of($sets, 'ArcanistLandCommitSet');
	+
	+ $revision_refs = mpull($sets, 'getRevisionRef');
	+ $viewer = $this->getViewer();
	+ $viewer_phid = $viewer->getPHID();
	+
	+ $unauthored = array();
	+ foreach ($revision_refs as $revision_ref) {
	+ $author_phid = $revision_ref->getAuthorPHID();
	+ if ($author_phid !== $viewer_phid) {
	+ $unauthored[] = $revision_ref;
	+ }
	+ }
	+
	+ if ($unauthored) {
	+ $this->getWorkflow()->loadHardpoints(
	+ $unauthored,
	+ array(
	+ ArcanistRevisionRef::HARDPOINT_AUTHORREF,
	+ ));
	+
	+ echo tsprintf(
	+ "\n%!\n%W\n\n",
	+ pht('NOT REVISION AUTHOR'),
	+ pht(
	+ 'You are landing revisions which you ("%s") are not the author of:',
	+ $viewer->getMonogram()));
	+
	+ foreach ($unauthored as $revision_ref) {
	+ $display_ref = $revision_ref->newDisplayRef();
	+
	+ $author_ref = $revision_ref->getAuthorRef();
	+ if ($author_ref) {
	+ $display_ref->appendLine(
	+ pht(
	+ 'Author: %s',
	+ $author_ref->getMonogram()));
	+ }
	+
	+ echo tsprintf('%s', $display_ref);
	+ }
	+
	+ echo tsprintf(
	+ "\n%?\n",
	+ pht(
	+ 'Use "Commandeer" in the web interface to become the author of '.
	+ 'a revision.'));
	+
	+ $query = pht('Land revisions you are not the author of?');
	+
	+ $this->getWorkflow()
	+ ->getPrompt('arc.land.unauthored')
	+ ->setQuery($query)
	+ ->execute();
	+ }
	+
	+ $planned = array();
	+ $closed = array();
	+ $not_accepted = array();
	+ foreach ($revision_refs as $revision_ref) {
	+ if ($revision_ref->isStatusChangesPlanned()) {
	+ $planned[] = $revision_ref;
	+ } else if ($revision_ref->isStatusClosed()) {
	+ $closed[] = $revision_ref;
	+ } else if (!$revision_ref->isStatusAccepted()) {
	+ $not_accepted[] = $revision_ref;
	+ }
	+ }
	+
	+ // See T10233. Previously, this prompt was bundled with the generic "not
	+ // accepted" prompt, but users found it confusing and interpreted the
	+ // prompt as a bug.
	+
	+ if ($planned) {
	+ $example_ref = head($planned);
	+
	+ echo tsprintf(
	+ "\n%!\n%W\n\n%W\n\n%W\n\n",
	+ pht('%s REVISION(S) HAVE CHANGES PLANNED', phutil_count($planned)),
	+ pht(
	+ 'You are landing %s revision(s) which are currently in the state '.
	+ '"%s", indicating that you expect to revise them before moving '.
	+ 'forward.',
	+ phutil_count($planned),
	+ $example_ref->getStatusDisplayName()),
	+ pht(
	+ 'Normally, you should update these %s revision(s), submit them '.
	+ 'for review, and wait for reviewers to accept them before '.
	+ 'you continue. To resubmit a revision for review, either: '.
	+ 'update the revision with revised changes; or use '.
	+ '"Request Review" from the web interface.',
	+ phutil_count($planned)),
	+ pht(
	+ 'These %s revision(s) have changes planned:',
	+ phutil_count($planned)));
	+
	+ foreach ($planned as $revision_ref) {
	+ echo tsprintf('%s', $revision_ref->newDisplayRef());
	+ }
	+
	+ $query = pht(
	+ 'Land %s revision(s) with changes planned?',
	+ phutil_count($planned));
	+
	+ $this->getWorkflow()
	+ ->getPrompt('arc.land.changes-planned')
	+ ->setQuery($query)
	+ ->execute();
	+ }
	+
	+ // See PHI1727. Previously, this prompt was bundled with the generic
	+ // "not accepted" prompt, but at least one user found it confusing.
	+
	+ if ($closed) {
	+ $example_ref = head($closed);
	+
	+ echo tsprintf(
	+ "\n%!\n%W\n\n",
	+ pht('%s REVISION(S) ARE ALREADY CLOSED', phutil_count($closed)),
	+ pht(
	+ 'You are landing %s revision(s) which are already in the state '.
	+ '"%s", indicating that they have previously landed:',
	+ phutil_count($closed),
	+ $example_ref->getStatusDisplayName()));
	+
	+ foreach ($closed as $revision_ref) {
	+ echo tsprintf('%s', $revision_ref->newDisplayRef());
	+ }
	+
	+ $query = pht(
	+ 'Land %s revision(s) that are already closed?',
	+ phutil_count($closed));
	+
	+ $this->getWorkflow()
	+ ->getPrompt('arc.land.closed')
	+ ->setQuery($query)
	+ ->execute();
	+ }
	+
	+ if ($not_accepted) {
	+ $example_ref = head($not_accepted);
	+
	+ echo tsprintf(
	+ "\n%!\n%W\n\n",
	+ pht('%s REVISION(S) ARE NOT ACCEPTED', phutil_count($not_accepted)),
	+ pht(
	+ 'You are landing %s revision(s) which are not in state "Accepted", '.
	+ 'indicating that they have not been accepted by reviewers. '.
	+ 'Normally, you should land changes only once they have been '.
	+ 'accepted. These revisions are in the wrong state:',
	+ phutil_count($not_accepted)));
	+
	+ foreach ($not_accepted as $revision_ref) {
	+ $display_ref = $revision_ref->newDisplayRef();
	+ $display_ref->appendLine(
	+ pht(
	+ 'Status: %s',
	+ $revision_ref->getStatusDisplayName()));
	+ echo tsprintf('%s', $display_ref);
	+ }
	+
	+ $query = pht(
	+ 'Land %s revision(s) in the wrong state?',
	+ phutil_count($not_accepted));
	+
	+ $this->getWorkflow()
	+ ->getPrompt('arc.land.not-accepted')
	+ ->setQuery($query)
	+ ->execute();
	+ }
	+
	+ $this->getWorkflow()->loadHardpoints(
	+ $revision_refs,
	+ array(
	+ ArcanistRevisionRef::HARDPOINT_PARENTREVISIONREFS,
	+ ));
	+
	+ $open_parents = array();
	+ foreach ($revision_refs as $revision_phid => $revision_ref) {
	+ $parent_refs = $revision_ref->getParentRevisionRefs();
	+ foreach ($parent_refs as $parent_ref) {
	+ $parent_phid = $parent_ref->getPHID();
	+
	+ // If we're landing a parent revision in this operation, we don't need
	+ // to complain that it hasn't been closed yet.
	+ if (isset($revision_refs[$parent_phid])) {
	+ continue;
	+ }
	+
	+ if ($parent_ref->isClosed()) {
	+ continue;
	+ }
	+
	+ if (!isset($open_parents[$parent_phid])) {
	+ $open_parents[$parent_phid] = array(
	+ 'ref' => $parent_ref,
	+ 'children' => array(),
	+ );
	+ }
	+
	+ $open_parents[$parent_phid]['children'][] = $revision_ref;
	+ }
	+ }
	+
	+ if ($open_parents) {
	+ echo tsprintf(
	+ "\n%!\n%W\n\n",
	+ pht('%s OPEN PARENT REVISION(S) ', phutil_count($open_parents)),
	+ pht(
	+ 'The changes you are landing depend on %s open parent revision(s). '.
	+ 'Usually, you should land parent revisions before landing the '.
	+ 'changes which depend on them. These parent revisions are open:',
	+ phutil_count($open_parents)));
	+
	+ foreach ($open_parents as $parent_phid => $spec) {
	+ $parent_ref = $spec['ref'];
	+
	+ $display_ref = $parent_ref->newDisplayRef();
	+
	+ $display_ref->appendLine(
	+ pht(
	+ 'Status: %s',
	+ $parent_ref->getStatusDisplayName()));
	+
	+ foreach ($spec['children'] as $child_ref) {
	+ $display_ref->appendLine(
	+ pht(
	+ 'Parent of: %s %s',
	+ $child_ref->getMonogram(),
	+ $child_ref->getName()));
	+ }
	+
	+ echo tsprintf('%s', $display_ref);
	+ }
	+
	+ $query = pht(
	+ 'Land changes that depend on %s open revision(s)?',
	+ phutil_count($open_parents));
	+
	+ $this->getWorkflow()
	+ ->getPrompt('arc.land.open-parents')
	+ ->setQuery($query)
	+ ->execute();
	+ }
	+
	+ $this->confirmBuilds($revision_refs);
	+
	+ // This is a reasonable place to bulk-load the commit messages, which
	+ // we'll need soon.
	+
	+ $this->getWorkflow()->loadHardpoints(
	+ $revision_refs,
	+ array(
	+ ArcanistRevisionRef::HARDPOINT_COMMITMESSAGE,
	+ ));
	+ }
	+
	+ private function confirmBuilds(array $revision_refs) {
	+ assert_instances_of($revision_refs, 'ArcanistRevisionRef');
	+
	+ $this->getWorkflow()->loadHardpoints(
	+ $revision_refs,
	+ array(
	+ ArcanistRevisionRef::HARDPOINT_BUILDABLEREF,
	+ ));
	+
	+ $buildable_refs = array();
	+ foreach ($revision_refs as $revision_ref) {
	+ $ref = $revision_ref->getBuildableRef();
	+ if ($ref) {
	+ $buildable_refs[] = $ref;
	+ }
	+ }
	+
	+ $this->getWorkflow()->loadHardpoints(
	+ $buildable_refs,
	+ array(
	+ ArcanistBuildableRef::HARDPOINT_BUILDREFS,
	+ ));
	+
	+ $build_refs = array();
	+ foreach ($buildable_refs as $buildable_ref) {
	+ foreach ($buildable_ref->getBuildRefs() as $build_ref) {
	+ $build_refs[] = $build_ref;
	+ }
	+ }
	+
	+ $this->getWorkflow()->loadHardpoints(
	+ $build_refs,
	+ array(
	+ ArcanistBuildRef::HARDPOINT_BUILDPLANREF,
	+ ));
	+
	+ $problem_builds = array();
	+ $has_failures = false;
	+ $has_ongoing = false;
	+
	+ $build_refs = msortv($build_refs, 'getStatusSortVector');
	+ foreach ($build_refs as $build_ref) {
	+ $plan_ref = $build_ref->getBuildPlanRef();
	+ if (!$plan_ref) {
	+ continue;
	+ }
	+
	+ $plan_behavior = $plan_ref->getBehavior('arc-land', 'always');
	+ $if_building = ($plan_behavior == 'building');
	+ $if_complete = ($plan_behavior == 'complete');
	+ $if_never = ($plan_behavior == 'never');
	+
	+ // If the build plan "Never" warns when landing, skip it.
	+ if ($if_never) {
	+ continue;
	+ }
	+
	+ // If the build plan warns when landing "If Complete" but the build is
	+ // not complete, skip it.
	+ if ($if_complete && !$build_ref->isComplete()) {
	+ continue;
	+ }
	+
	+ // If the build plan warns when landing "If Building" but the build is
	+ // complete, skip it.
	+ if ($if_building && $build_ref->isComplete()) {
	+ continue;
	+ }
	+
	+ // Ignore passing builds.
	+ if ($build_ref->isPassed()) {
	+ continue;
	+ }
	+
	+ if ($build_ref->isComplete()) {
	+ $has_failures = true;
	+ } else {
	+ $has_ongoing = true;
	+ }
	+
	+ $problem_builds[] = $build_ref;
	+ }
	+
	+ if (!$problem_builds) {
	+ return;
	+ }
	+
	+ $build_map = array();
	+ $failure_map = array();
	+ $buildable_map = mpull($buildable_refs, null, 'getPHID');
	+ $revision_map = mpull($revision_refs, null, 'getDiffPHID');
	+ foreach ($problem_builds as $build_ref) {
	+ $buildable_phid = $build_ref->getBuildablePHID();
	+ $buildable_ref = $buildable_map[$buildable_phid];
	+
	+ $object_phid = $buildable_ref->getObjectPHID();
	+ $revision_ref = $revision_map[$object_phid];
	+
	+ $revision_phid = $revision_ref->getPHID();
	+
	+ if (!isset($build_map[$revision_phid])) {
	+ $build_map[$revision_phid] = array(
	+ 'revisionRef' => $revision_phid,
	+ 'buildRefs' => array(),
	+ );
	+ }
	+
	+ $build_map[$revision_phid]['buildRefs'][] = $build_ref;
	+ }
	+
	+ $log = $this->getLogEngine();
	+
	+ if ($has_failures) {
	+ if ($has_ongoing) {
	+ $message = pht(
	+ '%s revision(s) have build failures or ongoing builds:',
	+ phutil_count($build_map));
	+
	+ $query = pht(
	+ 'Land %s revision(s) anyway, despite ongoing and failed builds?',
	+ phutil_count($build_map));
	+
	+ } else {
	+ $message = pht(
	+ '%s revision(s) have build failures:',
	+ phutil_count($build_map));
	+
	+ $query = pht(
	+ 'Land %s revision(s) anyway, despite failed builds?',
	+ phutil_count($build_map));
	+ }
	+
	+ echo tsprintf(
	+ "%!\n%s\n\n",
	+ pht('BUILD FAILURES'),
	+ $message);
	+
	+ $prompt_key = 'arc.land.failed-builds';
	+ } else if ($has_ongoing) {
	+ echo tsprintf(
	+ "%!\n%s\n\n",
	+ pht('ONGOING BUILDS'),
	+ pht(
	+ '%s revision(s) have ongoing builds:',
	+ phutil_count($build_map)));
	+
	+ $query = pht(
	+ 'Land %s revision(s) anyway, despite ongoing builds?',
	+ phutil_count($build_map));
	+
	+ $prompt_key = 'arc.land.ongoing-builds';
	+ }
	+
	+ echo tsprintf("\n");
	+ foreach ($build_map as $build_item) {
	+ $revision_ref = $build_item['revisionRef'];
	+
	+ echo tsprintf('%s', $revision_ref->newDisplayRef());
	+
	+ foreach ($build_item['buildRefs'] as $build_ref) {
	+ echo tsprintf('%s', $build_ref->newDisplayRef());
	+ }
	+
	+ echo tsprintf("\n");
	+ }
	+
	+ echo tsprintf(
	+ "\n%s\n\n",
	+ pht('You can review build details here:'));
	+
	+ // TODO: Only show buildables with problem builds.
	+
	+ foreach ($buildable_refs as $buildable) {
	+ $display_ref = $buildable->newDisplayRef();
	+
	+ // TODO: Include URI here.
	+
	+ echo tsprintf('%s', $display_ref);
	+ }
	+
	+ $this->getWorkflow()
	+ ->getPrompt($prompt_key)
	+ ->setQuery($query)
	+ ->execute();
	+ }
	+
	+ final protected function confirmImplicitCommits(array $sets, array $symbols) {
	+ assert_instances_of($sets, 'ArcanistLandCommitSet');
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+
	+ $implicit = array();
	+ foreach ($sets as $set) {
	+ if ($set->hasImplicitCommits()) {
	+ $implicit[] = $set;
	+ }
	+ }
	+
	+ if (!$implicit) {
	+ return;
	+ }
	+
	+ echo tsprintf(
	+ "\n%!\n%W\n",
	+ pht('IMPLICIT COMMITS'),
	+ pht(
	+ 'Some commits reachable from the specified sources (%s) are not '.
	+ 'associated with revisions, and may not have been reviewed. These '.
	+ 'commits will be landed as though they belong to the nearest '.
	+ 'ancestor revision:',
	+ $this->getDisplaySymbols($symbols)));
	+
	+ foreach ($implicit as $set) {
	+ $this->printCommitSet($set);
	+ }
	+
	+ $query = pht(
	+ 'Continue with this mapping between commits and revisions?');
	+
	+ $this->getWorkflow()
	+ ->getPrompt('arc.land.implicit')
	+ ->setQuery($query)
	+ ->execute();
	+ }
	+
	+ final protected function getDisplaySymbols(array $symbols) {
	+ $display = array();
	+
	+ foreach ($symbols as $symbol) {
	+ $display[] = sprintf('"%s"', addcslashes($symbol->getSymbol(), '\\"'));
	+ }
	+
	+ return implode(', ', $display);
	+ }
	+
	+ final protected function printCommitSet(ArcanistLandCommitSet $set) {
	+ $revision_ref = $set->getRevisionRef();
	+
	+ echo tsprintf(
	+ "\n%s",
	+ $revision_ref->newDisplayRef());
	+
	+ foreach ($set->getCommits() as $commit) {
	+ $is_implicit = $commit->getIsImplicitCommit();
	+
	+ $display_hash = $this->getDisplayHash($commit->getHash());
	+ $display_summary = $commit->getDisplaySummary();
	+
	+ if ($is_implicit) {
	+ echo tsprintf(
	+ " <bg:yellow> %s </bg> %s\n",
	+ $display_hash,
	+ $display_summary);
	+ } else {
	+ echo tsprintf(
	+ " %s %s\n",
	+ $display_hash,
	+ $display_summary);
	+ }
	+ }
	+ }
	+
	+ final protected function loadRevisionRefs(array $commit_map) {
	+ assert_instances_of($commit_map, 'ArcanistLandCommit');
	+ $workflow = $this->getWorkflow();
	+
	+ $state_refs = array();
	+ foreach ($commit_map as $commit) {
	+ $hash = $commit->getHash();
	+
	+ $commit_ref = id(new ArcanistCommitRef())
	+ ->setCommitHash($hash);
	+
	+ $state_ref = id(new ArcanistWorkingCopyStateRef())
	+ ->setCommitRef($commit_ref);
	+
	+ $state_refs[$hash] = $state_ref;
	+ }
	+
	+ $force_symbol_ref = $this->getRevisionSymbolRef();
	+ $force_ref = null;
	+ if ($force_symbol_ref) {
	+ $workflow->loadHardpoints(
	+ $force_symbol_ref,
	+ ArcanistSymbolRef::HARDPOINT_OBJECT);
	+
	+ $force_ref = $force_symbol_ref->getObject();
	+ if (!$force_ref) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Symbol "%s" does not identify a valid revision.',
	+ $force_symbol_ref->getSymbol()));
	+ }
	+ }
	+
	+ $workflow->loadHardpoints(
	+ $state_refs,
	+ ArcanistWorkingCopyStateRef::HARDPOINT_REVISIONREFS);
	+
	+ foreach ($commit_map as $commit) {
	+ $hash = $commit->getHash();
	+ $state_ref = $state_refs[$hash];
	+
	+ $revision_refs = $state_ref->getRevisionRefs();
	+
	+ // If we have several possible revisions but one of them matches the
	+ // "--revision" argument, just select it. This is relatively safe and
	+ // reasonable and doesn't need a warning.
	+
	+ if ($force_ref) {
	+ if (count($revision_refs) > 1) {
	+ foreach ($revision_refs as $revision_ref) {
	+ if ($revision_ref->getPHID() === $force_ref->getPHID()) {
	+ $revision_refs = array($revision_ref);
	+ break;
	+ }
	+ }
	+ }
	+ }
	+
	+ if (count($revision_refs) === 1) {
	+ $revision_ref = head($revision_refs);
	+ $commit->setExplicitRevisionRef($revision_ref);
	+ continue;
	+ }
	+
	+ if (!$revision_refs) {
	+ continue;
	+ }
	+
	+ // TODO: If we have several refs but all but one are abandoned or closed
	+ // or authored by someone else, we could guess what you mean.
	+
	+ $symbols = $commit->getSymbols();
	+ $raw_symbols = mpull($symbols, 'getSymbol');
	+ $symbol_list = implode(', ', $raw_symbols);
	+ $display_hash = $this->getDisplayHash($hash);
	+
	+ // TODO: Include "use 'arc look --type commit abc' to figure out why"
	+ // once that works?
	+
	+ echo tsprintf(
	+ "\n%!\n%W\n\n",
	+ pht('AMBIGUOUS REVISION'),
	+ pht(
	+ 'The revision associated with commit "%s" (an ancestor of: %s) '.
	+ 'is ambiguous. These %s revision(s) are associated with the commit:',
	+ $display_hash,
	+ implode(', ', $raw_symbols),
	+ phutil_count($revision_refs)));
	+
	+ foreach ($revision_refs as $revision_ref) {
	+ echo tsprintf(
	+ '%s',
	+ $revision_ref->newDisplayRef());
	+ }
	+
	+ echo tsprintf("\n");
	+
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Revision for commit "%s" is ambiguous. Use "--revision" to force '.
	+ 'selection of a particular revision.',
	+ $display_hash));
	+ }
	+
	+ // TODO: Some of the revisions we've identified may be mapped to an
	+ // outdated set of commits. We should look in local branches for a better
	+ // set of commits, and try to confirm that the state we're about to land
	+ // is the current state in Differential.
	+
	+ if ($force_ref) {
	+ $phid_map = array();
	+ foreach ($commit_map as $commit) {
	+ $explicit_ref = $commit->getExplicitRevisionRef();
	+ if ($explicit_ref) {
	+ $revision_phid = $explicit_ref->getPHID();
	+ $phid_map[$revision_phid] = $revision_phid;
	+ }
	+ }
	+
	+ $force_phid = $force_ref->getPHID();
	+
	+ // If none of the commits have a revision, forcing the revision is
	+ // reasonable and we don't need to confirm it.
	+
	+ // If some of the commits have a revision, but it's the same as the
	+ // revision we're forcing, forcing the revision is also reasonable.
	+
	+ // Discard the revision we're trying to force, then check if there's
	+ // anything left. If some of the commits have a different revision,
	+ // make sure the user is really doing what they expect.
	+
	+ unset($phid_map[$force_phid]);
	+
	+ if ($phid_map) {
	+ // TODO: Make this more clear.
	+
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'TODO: You are forcing a revision, but commits are associated '.
	+ 'with some other revision. Are you REALLY sure you want to land '.
	+ 'ALL these commits wiht a different unrelated revision???'));
	+ }
	+
	+ foreach ($commit_map as $commit) {
	+ $commit->setExplicitRevisionRef($force_ref);
	+ }
	+ }
	+ }
	+
	+ final protected function getDisplayHash($hash) {
	+ // TODO: This should be on the API object.
	+ return substr($hash, 0, 12);
	+ }
	+
	+ final protected function confirmCommits(
	+ $into_commit,
	+ array $symbols,
	+ array $commit_map) {
	+
	+ $commit_count = count($commit_map);
	+
	+ if (!$commit_count) {
	+ $message = pht(
	+ 'There are no commits reachable from the specified sources (%s) '.
	+ 'which are not already present in the state you are merging '.
	+ 'into ("%s"), so nothing can land.',
	+ $this->getDisplaySymbols($symbols),
	+ $this->getDisplayHash($into_commit));
	+
	+ echo tsprintf(
	+ "\n%!\n%W\n\n",
	+ pht('NOTHING TO LAND'),
	+ $message);
	+
	+ throw new PhutilArgumentUsageException(
	+ pht('There are no commits to land.'));
	+ }
	+
	+ // Reverse the commit list so that it's oldest-first, since this is the
	+ // order we'll use to show revisions.
	+ $commit_map = array_reverse($commit_map, true);
	+
	+ $warn_limit = $this->getWorkflow()->getLargeWorkingSetLimit();
	+ $show_limit = 5;
	+ if ($commit_count > $warn_limit) {
	+ if ($into_commit === null) {
	+ $message = pht(
	+ 'There are %s commit(s) reachable from the specified sources (%s). '.
	+ 'You are landing into the empty state, so all of these commits '.
	+ 'will land:',
	+ new PhutilNumber($commit_count),
	+ $this->getDisplaySymbols($symbols));
	+ } else {
	+ $message = pht(
	+ 'There are %s commit(s) reachable from the specified sources (%s) '.
	+ 'that are not present in the repository state you are merging '.
	+ 'into ("%s"). All of these commits will land:',
	+ new PhutilNumber($commit_count),
	+ $this->getDisplaySymbols($symbols),
	+ $this->getDisplayHash($into_commit));
	+ }
	+
	+ echo tsprintf(
	+ "\n%!\n%W\n",
	+ pht('LARGE WORKING SET'),
	+ $message);
	+
	+ $display_commits = array_merge(
	+ array_slice($commit_map, 0, $show_limit),
	+ array(null),
	+ array_slice($commit_map, -$show_limit));
	+
	+ echo tsprintf("\n");
	+
	+ foreach ($display_commits as $commit) {
	+ if ($commit === null) {
	+ echo tsprintf(
	+ " %s\n",
	+ pht(
	+ '< ... %s more commits ... >',
	+ new PhutilNumber($commit_count - ($show_limit * 2))));
	+ } else {
	+ echo tsprintf(
	+ " %s %s\n",
	+ $this->getDisplayHash($commit->getHash()),
	+ $commit->getDisplaySummary());
	+ }
	+ }
	+
	+ $query = pht(
	+ 'Land %s commit(s)?',
	+ new PhutilNumber($commit_count));
	+
	+ $this->getWorkflow()
	+ ->getPrompt('arc.land.large-working-set')
	+ ->setQuery($query)
	+ ->execute();
	+ }
	+
	+ // Build the commit objects into a tree.
	+ foreach ($commit_map as $commit_hash => $commit) {
	+ $parent_map = array();
	+ foreach ($commit->getParents() as $parent) {
	+ if (isset($commit_map[$parent])) {
	+ $parent_map[$parent] = $commit_map[$parent];
	+ }
	+ }
	+ $commit->setParentCommits($parent_map);
	+ }
	+
	+ // Identify the commits which are heads (have no children).
	+ $child_map = array();
	+ foreach ($commit_map as $commit_hash => $commit) {
	+ foreach ($commit->getParents() as $parent) {
	+ $child_map[$parent][$commit_hash] = $commit;
	+ }
	+ }
	+
	+ foreach ($commit_map as $commit_hash => $commit) {
	+ if (isset($child_map[$commit_hash])) {
	+ continue;
	+ }
	+ $commit->setIsHeadCommit(true);
	+ }
	+
	+ return $commit_map;
	+ }
	+
	+ public function execute() {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ $this->validateArguments();
	+
	+ $raw_symbols = $this->getSourceRefs();
	+ if (!$raw_symbols) {
	+ $raw_symbols = $this->getDefaultSymbols();
	+ }
	+
	+ $symbols = array();
	+ foreach ($raw_symbols as $raw_symbol) {
	+ $symbols[] = id(new ArcanistLandSymbol())
	+ ->setSymbol($raw_symbol);
	+ }
	+
	+ $this->resolveSymbols($symbols);
	+
	+ $onto_remote = $this->selectOntoRemote($symbols);
	+ $this->setOntoRemote($onto_remote);
	+
	+ $onto_refs = $this->selectOntoRefs($symbols);
	+ $this->confirmOntoRefs($onto_refs);
	+ $this->setOntoRefs($onto_refs);
	+
	+ $this->selectIntoRemote();
	+ $this->selectIntoRef();
	+
	+ $into_commit = $this->selectIntoCommit();
	+ $commit_map = $this->selectCommits($into_commit, $symbols);
	+
	+ $this->loadRevisionRefs($commit_map);
	+
	+ // TODO: It's possible we have a list of commits which includes disjoint
	+ // groups of commits associated with the same revision, or groups of
	+ // commits which do not form a range. We should test that here, since we
	+ // can't land commit groups which are not a single contiguous range.
	+
	+ $revision_groups = array();
	+ foreach ($commit_map as $commit_hash => $commit) {
	+ $revision_ref = $commit->getRevisionRef();
	+
	+ if (!$revision_ref) {
	+ echo tsprintf(
	+ "\n%!\n%W\n\n",
	+ pht('UNKNOWN REVISION'),
	+ pht(
	+ 'Unable to determine which revision is associated with commit '.
	+ '"%s". Use "arc diff" to create or update a revision with this '.
	+ 'commit, or "--revision" to force selection of a particular '.
	+ 'revision.',
	+ $this->getDisplayHash($commit_hash)));
	+
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Unable to determine revision for commit "%s".',
	+ $this->getDisplayHash($commit_hash)));
	+ }
	+
	+ $revision_groups[$revision_ref->getPHID()][] = $commit;
	+ }
	+
	+ $commit_heads = array();
	+ foreach ($commit_map as $commit) {
	+ if ($commit->getIsHeadCommit()) {
	+ $commit_heads[] = $commit;
	+ }
	+ }
	+
	+ $revision_order = array();
	+ foreach ($commit_heads as $head) {
	+ foreach ($head->getAncestorRevisionPHIDs() as $phid) {
	+ $revision_order[$phid] = true;
	+ }
	+ }
	+
	+ $revision_groups = array_select_keys(
	+ $revision_groups,
	+ array_keys($revision_order));
	+
	+ $sets = array();
	+ foreach ($revision_groups as $revision_phid => $group) {
	+ $revision_ref = head($group)->getRevisionRef();
	+
	+ $set = id(new ArcanistLandCommitSet())
	+ ->setRevisionRef($revision_ref)
	+ ->setCommits($group);
	+
	+ $sets[$revision_phid] = $set;
	+ }
	+
	+ if (!$this->getShouldPreview()) {
	+ $this->confirmImplicitCommits($sets, $symbols);
	+ }
	+
	+ $log->writeStatus(
	+ pht('LANDING'),
	+ pht('These changes will land:'));
	+
	+ foreach ($sets as $set) {
	+ $this->printCommitSet($set);
	+ }
	+
	+ if ($this->getShouldPreview()) {
	+ $log->writeStatus(
	+ pht('PREVIEW'),
	+ pht('Completed preview of land operation.'));
	+ return;
	+ }
	+
	+ $query = pht('Land these changes?');
	+ $this->getWorkflow()
	+ ->getPrompt('arc.land.confirm')
	+ ->setQuery($query)
	+ ->execute();
	+
	+ $this->confirmRevisions($sets);
	+
	+ $workflow = $this->getWorkflow();
	+
	+ $is_incremental = $this->getIsIncremental();
	+ $is_hold = $this->getShouldHold();
	+ $is_keep = $this->getShouldKeep();
	+
	+ $local_state = $api->newLocalState()
	+ ->setWorkflow($workflow)
	+ ->saveLocalState();
	+
	+ $seen_into = array();
	+ try {
	+ $last_key = last_key($sets);
	+
	+ $need_cascade = array();
	+ $need_prune = array();
	+
	+ foreach ($sets as $set_key => $set) {
	+ // Add these first, so we don't add them multiple times if we need
	+ // to retry a push.
	+ $need_prune[] = $set;
	+ $need_cascade[] = $set;
	+
	+ while (true) {
	+ $into_commit = $this->executeMerge($set, $into_commit);
	+
	+ if ($is_hold) {
	+ $should_push = false;
	+ } else if ($is_incremental) {
	+ $should_push = true;
	+ } else {
	+ $is_last = ($set_key === $last_key);
	+ $should_push = $is_last;
	+ }
	+
	+ if ($should_push) {
	+ try {
	+ $this->pushChange($into_commit);
	+ } catch (Exception $ex) {
	+
	+ // TODO: If the push fails, fetch and retry if the remote ref
	+ // has moved ahead of us.
	+
	+ if ($this->getIntoLocal()) {
	+ $can_retry = false;
	+ } else if ($this->getIntoEmpty()) {
	+ $can_retry = false;
	+ } else if ($this->getIntoRemote() !== $this->getOntoRemote()) {
	+ $can_retry = false;
	+ } else {
	+ $can_retry = false;
	+ }
	+
	+ if ($can_retry) {
	+ // New commit state here
	+ $into_commit = '..';
	+ continue;
	+ }
	+
	+ throw $ex;
	+ }
	+
	+ if ($need_cascade) {
	+
	+ // NOTE: We cascade each set we've pushed, but we're going to
	+ // cascade them from most recent to least recent. This way,
	+ // branches which descend from more recent changes only cascade
	+ // once, directly in to the correct state.
	+
	+ $need_cascade = array_reverse($need_cascade);
	+ foreach ($need_cascade as $cascade_set) {
	+ $this->cascadeState($set, $into_commit);
	+ }
	+ $need_cascade = array();
	+ }
	+
	+ if (!$is_keep) {
	+ $this->pruneBranches($need_prune);
	+ $need_prune = array();
	+ }
	+ }
	+
	+ break;
	+ }
	+ }
	+
	+ if ($is_hold) {
	+ $this->didHoldChanges();
	+ $this->discardLocalState();
	+ } else {
	+ $this->reconcileLocalState($into_commit, $local_state);
	+ }
	+
	+ // TODO: Restore this.
	+ // $this->getWorkflow()->askForRepositoryUpdate();
	+
	+ $log->writeSuccess(
	+ pht('DONE'),
	+ pht('Landed changes.'));
	+ } catch (Exception $ex) {
	+ $local_state->restoreLocalState();
	+ throw $ex;
	+ } catch (Throwable $ex) {
	+ $local_state->restoreLocalState();
	+ throw $ex;
	+ }
	+ }
	+
	+
	+ protected function validateArguments() {
	+ $log = $this->getLogEngine();
	+
	+ $into_local = $this->getIntoLocalArgument();
	+ $into_empty = $this->getIntoEmptyArgument();
	+ $into_remote = $this->getIntoRemoteArgument();
	+
	+ $into_count = 0;
	+ if ($into_remote !== null) {
	+ $into_count++;
	+ }
	+
	+ if ($into_local) {
	+ $into_count++;
	+ }
	+
	+ if ($into_empty) {
	+ $into_count++;
	+ }
	+
	+ if ($into_count > 1) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Arguments "--into-local", "--into-remote", and "--into-empty" '.
	+ 'are mutually exclusive.'));
	+ }
	+
	+ $into = $this->getIntoArgument();
	+ if ($into && ($into_empty !== null)) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Arguments "--into" and "--into-empty" are mutually exclusive.'));
	+ }
	+
	+ $strategy = $this->selectMergeStrategy();
	+ $this->setStrategy($strategy);
	+
	+ // Build the symbol ref here (which validates the format of the symbol),
	+ // but don't load the object until later on when we're sure we actually
	+ // need it, since loading it requires a relatively expensive Conduit call.
	+ $revision_symbol = $this->getRevisionSymbol();
	+ if ($revision_symbol) {
	+ $symbol_ref = id(new ArcanistRevisionSymbolRef())
	+ ->setSymbol($revision_symbol);
	+ $this->setRevisionSymbolRef($symbol_ref);
	+ }
	+
	+ // NOTE: When a user provides: "--hold" or "--preview"; and "--incremental"
	+ // or various combinations of remote flags, the flags affecting push/remote
	+ // behavior have no effect.
	+
	+ // These combinations are allowed to support adding "--preview" or "--hold"
	+ // to any command to run the same command with fewer side effects.
	+ }
	+
	+ abstract protected function getDefaultSymbols();
	+ abstract protected function resolveSymbols(array $symbols);
	+ abstract protected function selectOntoRemote(array $symbols);
	+ abstract protected function selectOntoRefs(array $symbols);
	+ abstract protected function confirmOntoRefs(array $onto_refs);
	+ abstract protected function selectIntoRemote();
	+ abstract protected function selectIntoRef();
	+ abstract protected function selectIntoCommit();
	+ abstract protected function selectCommits($into_commit, array $symbols);
	+ abstract protected function executeMerge(
	+ ArcanistLandCommitSet $set,
	+ $into_commit);
	+ abstract protected function pushChange($into_commit);
	+ abstract protected function cascadeState(
	+ ArcanistLandCommitSet $set,
	+ $into_commit);
	+
	+ protected function isSquashStrategy() {
	+ return ($this->getStrategy() === 'squash');
	+ }
	+
	+ abstract protected function pruneBranches(array $sets);
	+
	+ abstract protected function reconcileLocalState(
	+ $into_commit,
	+ ArcanistRepositoryLocalState $state);
	+
	+ private function selectMergeStrategy() {
	+ $log = $this->getLogEngine();
	+
	+ $supported_strategies = array(
	+ 'merge',
	+ 'squash',
	+ );
	+ $supported_strategies = array_fuse($supported_strategies);
	+ $strategy_list = implode(', ', $supported_strategies);
	+
	+ $strategy = $this->getStrategyArgument();
	+ if ($strategy !== null) {
	+ if (!isset($supported_strategies[$strategy])) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Merge strategy "%s" specified with "--strategy" is unknown. '.
	+ 'Supported merge strategies are: %s.',
	+ $strategy,
	+ $strategy_list));
	+ }
	+
	+ $log->writeStatus(
	+ pht('STRATEGY'),
	+ pht(
	+ 'Merging with "%s" strategy, selected with "--strategy".',
	+ $strategy));
	+
	+ return $strategy;
	+ }
	+
	+ $strategy_key = 'arc.land.strategy';
	+ $strategy = $this->getWorkflow()->getConfig($strategy_key);
	+ if ($strategy !== null) {
	+ if (!isset($supported_strategies[$strategy])) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Merge strategy "%s" specified in "%s" configuration is '.
	+ 'unknown. Supported merge strategies are: %s.',
	+ $strategy,
	+ $strategy_list));
	+ }
	+
	+ $log->writeStatus(
	+ pht('STRATEGY'),
	+ pht(
	+ 'Merging with "%s" strategy, configured with "%s".',
	+ $strategy,
	+ $strategy_key));
	+
	+ return $strategy;
	+ }
	+
	+ $strategy = 'squash';
	+
	+ $log->writeStatus(
	+ pht('STRATEGY'),
	+ pht(
	+ 'Merging with "%s" strategy, the default strategy.',
	+ $strategy));
	+
	+ return $strategy;
	+ }
	+
	+}
	diff --git a/src/land/engine/ArcanistMercurialLandEngine.php b/src/land/engine/ArcanistMercurialLandEngine.php
	new file mode 100644
	--- /dev/null
	+++ b/src/land/engine/ArcanistMercurialLandEngine.php
	@@ -0,0 +1,603 @@
	+<?php
	+
	+final class ArcanistMercurialLandEngine
	+ extends ArcanistLandEngine {
	+
	+ protected function getDefaultSymbols() {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ $bookmark = $api->getActiveBookmark();
	+ if ($bookmark !== null) {
	+
	+ $log->writeStatus(
	+ pht('SOURCE'),
	+ pht(
	+ 'Landing the active bookmark, "%s".',
	+ $bookmark));
	+
	+ return array($bookmark);
	+ }
	+
	+ $branch = $api->getBranchName();
	+ if ($branch !== null) {
	+
	+ $log->writeStatus(
	+ pht('SOURCE'),
	+ pht(
	+ 'Landing the current branch, "%s".',
	+ $branch));
	+
	+ return array($branch);
	+ }
	+
	+ throw new Exception(pht('TODO: Operate on raw revision.'));
	+ }
	+
	+ protected function resolveSymbols(array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $api = $this->getRepositoryAPI();
	+
	+ foreach ($symbols as $symbol) {
	+ $raw_symbol = $symbol->getSymbol();
	+
	+ if ($api->isBookmark($raw_symbol)) {
	+ $hash = $api->getBookmarkCommitHash($raw_symbol);
	+ $symbol->setCommit($hash);
	+
	+ // TODO: Set that this is a bookmark?
	+
	+ continue;
	+ }
	+
	+ if ($api->isBranch($raw_symbol)) {
	+ $hash = $api->getBranchCommitHash($raw_symbol);
	+ $symbol->setCommit($hash);
	+
	+ // TODO: Set that this is a branch?
	+
	+ continue;
	+ }
	+
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Symbol "%s" is not a bookmark or branch name.',
	+ $raw_symbol));
	+ }
	+ }
	+
	+ protected function selectOntoRemote(array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $remote = $this->newOntoRemote($symbols);
	+
	+ // TODO: Verify this remote actually exists.
	+
	+ return $remote;
	+ }
	+
	+ private function newOntoRemote(array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ $remote = $this->getOntoRemoteArgument();
	+ if ($remote !== null) {
	+
	+ $log->writeStatus(
	+ pht('ONTO REMOTE'),
	+ pht(
	+ 'Remote "%s" was selected with the "--onto-remote" flag.',
	+ $remote));
	+
	+ return $remote;
	+ }
	+
	+ $remote = $this->getOntoRemoteFromConfiguration();
	+ if ($remote !== null) {
	+ $remote_key = $this->getOntoRemoteConfigurationKey();
	+
	+ $log->writeStatus(
	+ pht('ONTO REMOTE'),
	+ pht(
	+ 'Remote "%s" was selected by reading "%s" configuration.',
	+ $remote,
	+ $remote_key));
	+
	+ return $remote;
	+ }
	+
	+ $api = $this->getRepositoryAPI();
	+
	+ $default_remote = 'default';
	+
	+ $log->writeStatus(
	+ pht('ONTO REMOTE'),
	+ pht(
	+ 'Landing onto remote "%s", the default remote under Mercurial.',
	+ $default_remote));
	+
	+ return $default_remote;
	+ }
	+
	+ protected function selectOntoRefs(array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $log = $this->getLogEngine();
	+
	+ $onto = $this->getOntoArguments();
	+ if ($onto) {
	+
	+ $log->writeStatus(
	+ pht('ONTO TARGET'),
	+ pht(
	+ 'Refs were selected with the "--onto" flag: %s.',
	+ implode(', ', $onto)));
	+
	+ return $onto;
	+ }
	+
	+ $onto = $this->getOntoFromConfiguration();
	+ if ($onto) {
	+ $onto_key = $this->getOntoConfigurationKey();
	+
	+ $log->writeStatus(
	+ pht('ONTO TARGET'),
	+ pht(
	+ 'Refs were selected by reading "%s" configuration: %s.',
	+ $onto_key,
	+ implode(', ', $onto)));
	+
	+ return $onto;
	+ }
	+
	+ $api = $this->getRepositoryAPI();
	+
	+ $default_onto = 'default';
	+
	+ $log->writeStatus(
	+ pht('ONTO TARGET'),
	+ pht(
	+ 'Landing onto target "%s", the default target under Mercurial.',
	+ $default_onto));
	+
	+ return array($default_onto);
	+ }
	+
	+ protected function confirmOntoRefs(array $onto_refs) {
	+ foreach ($onto_refs as $onto_ref) {
	+ if (!strlen($onto_ref)) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Selected "onto" ref "%s" is invalid: the empty string is not '.
	+ 'a valid ref.',
	+ $onto_ref));
	+ }
	+ }
	+ }
	+
	+ protected function selectIntoRemote() {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ if ($this->getIntoEmptyArgument()) {
	+ $this->setIntoEmpty(true);
	+
	+ $log->writeStatus(
	+ pht('INTO REMOTE'),
	+ pht(
	+ 'Will merge into empty state, selected with the "--into-empty" '.
	+ 'flag.'));
	+
	+ return;
	+ }
	+
	+ if ($this->getIntoLocalArgument()) {
	+ $this->setIntoLocal(true);
	+
	+ $log->writeStatus(
	+ pht('INTO REMOTE'),
	+ pht(
	+ 'Will merge into local state, selected with the "--into-local" '.
	+ 'flag.'));
	+
	+ return;
	+ }
	+
	+ $into = $this->getIntoRemoteArgument();
	+ if ($into !== null) {
	+
	+ // TODO: Verify that this is a valid path.
	+ // TODO: Allow a raw URI?
	+
	+ $this->setIntoRemote($into);
	+
	+ $log->writeStatus(
	+ pht('INTO REMOTE'),
	+ pht(
	+ 'Will merge into remote "%s", selected with the "--into" flag.',
	+ $into));
	+
	+ return;
	+ }
	+
	+ $onto = $this->getOntoRemote();
	+ $this->setIntoRemote($onto);
	+
	+ $log->writeStatus(
	+ pht('INTO REMOTE'),
	+ pht(
	+ 'Will merge into remote "%s" by default, because this is the remote '.
	+ 'the change is landing onto.',
	+ $onto));
	+ }
	+
	+ protected function selectIntoRef() {
	+ $log = $this->getLogEngine();
	+
	+ if ($this->getIntoEmptyArgument()) {
	+ $log->writeStatus(
	+ pht('INTO TARGET'),
	+ pht(
	+ 'Will merge into empty state, selected with the "--into-empty" '.
	+ 'flag.'));
	+
	+ return;
	+ }
	+
	+ $into = $this->getIntoArgument();
	+ if ($into !== null) {
	+ $this->setIntoRef($into);
	+
	+ $log->writeStatus(
	+ pht('INTO TARGET'),
	+ pht(
	+ 'Will merge into target "%s", selected with the "--into" flag.',
	+ $into));
	+
	+ return;
	+ }
	+
	+ $ontos = $this->getOntoRefs();
	+ $onto = head($ontos);
	+
	+ $this->setIntoRef($onto);
	+ if (count($ontos) > 1) {
	+ $log->writeStatus(
	+ pht('INTO TARGET'),
	+ pht(
	+ 'Will merge into target "%s" by default, because this is the first '.
	+ '"onto" target.',
	+ $onto));
	+ } else {
	+ $log->writeStatus(
	+ pht('INTO TARGET'),
	+ pht(
	+ 'Will merge into target "%s" by default, because this is the "onto" '.
	+ 'target.',
	+ $onto));
	+ }
	+ }
	+
	+ protected function selectIntoCommit() {
	+ // Make sure that our "into" target is valid.
	+ $log = $this->getLogEngine();
	+
	+ if ($this->getIntoEmpty()) {
	+ // If we're running under "--into-empty", we don't have to do anything.
	+
	+ $log->writeStatus(
	+ pht('INTO COMMIT'),
	+ pht('Preparing merge into the empty state.'));
	+
	+ return null;
	+ }
	+
	+ if ($this->getIntoLocal()) {
	+ // If we're running under "--into-local", just make sure that the
	+ // target identifies some actual commit.
	+ $api = $this->getRepositoryAPI();
	+ $local_ref = $this->getIntoRef();
	+
	+ // TODO: This error handling could probably be cleaner.
	+
	+ $into_commit = $api->getCanonicalRevisionName($local_ref);
	+
	+ $log->writeStatus(
	+ pht('INTO COMMIT'),
	+ pht(
	+ 'Preparing merge into local target "%s", at commit "%s".',
	+ $local_ref,
	+ $this->getDisplayHash($into_commit)));
	+
	+ return $into_commit;
	+ }
	+
	+ $target = id(new ArcanistLandTarget())
	+ ->setRemote($this->getIntoRemote())
	+ ->setRef($this->getIntoRef());
	+
	+ $commit = $this->fetchTarget($target);
	+ if ($commit !== null) {
	+ $log->writeStatus(
	+ pht('INTO COMMIT'),
	+ pht(
	+ 'Preparing merge into "%s" from remote "%s", at commit "%s".',
	+ $target->getRef(),
	+ $target->getRemote(),
	+ $this->getDisplayHash($commit)));
	+ return $commit;
	+ }
	+
	+ // If we have no valid target and the user passed "--into" explicitly,
	+ // treat this as an error. For example, "arc land --into Q --onto Q",
	+ // where "Q" does not exist, is an error.
	+ if ($this->getIntoArgument()) {
	+ throw new PhutilArgumentUsageException(
	+ pht(
	+ 'Ref "%s" does not exist in remote "%s".',
	+ $target->getRef(),
	+ $target->getRemote()));
	+ }
	+
	+ // Otherwise, treat this as implying "--into-empty". For example,
	+ // "arc land --onto Q", where "Q" does not exist, is equivalent to
	+ // "arc land --into-empty --onto Q".
	+ $this->setIntoEmpty(true);
	+
	+ $log->writeStatus(
	+ pht('INTO COMMIT'),
	+ pht(
	+ 'Preparing merge into the empty state to create target "%s" '.
	+ 'in remote "%s".',
	+ $target->getRef(),
	+ $target->getRemote()));
	+
	+ return null;
	+ }
	+
	+ private function fetchTarget(ArcanistLandTarget $target) {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ // TODO: Support bookmarks.
	+ // TODO: Deal with bookmark save/restore behavior.
	+ // TODO: Format this nicely with passthru.
	+ // TODO: Raise a good error message when the ref does not exist.
	+
	+ $api->execPassthru(
	+ 'pull -b %s -- %s',
	+ $target->getRef(),
	+ $target->getRemote());
	+
	+ // TODO: Deal with multiple branch heads.
	+
	+ list($stdout) = $api->execxLocal(
	+ 'log --rev %s --template %s --',
	+ hgsprintf(
	+ 'last(ancestors(%s) and !outgoing(%s))',
	+ $target->getRef(),
	+ $target->getRemote()),
	+ '{node}');
	+
	+ return trim($stdout);
	+ }
	+
	+ protected function selectCommits($into_commit, array $symbols) {
	+ assert_instances_of($symbols, 'ArcanistLandSymbol');
	+ $api = $this->getRepositoryAPI();
	+
	+ $commit_map = array();
	+ foreach ($symbols as $symbol) {
	+ $symbol_commit = $symbol->getCommit();
	+ $template = '{node}-{parents}-';
	+
	+ if ($into_commit === null) {
	+ list($commits) = $api->execxLocal(
	+ 'log --rev %s --template %s --',
	+ hgsprintf('reverse(ancestors(%s))', $into_commit),
	+ $template);
	+ } else {
	+ list($commits) = $api->execxLocal(
	+ 'log --rev %s --template %s --',
	+ hgsprintf(
	+ 'reverse(ancestors(%s) - ancestors(%s))',
	+ $symbol_commit,
	+ $into_commit),
	+ $template);
	+ }
	+
	+ $commits = phutil_split_lines($commits, false);
	+ foreach ($commits as $line) {
	+ if (!strlen($line)) {
	+ continue;
	+ }
	+
	+ $parts = explode('-', $line, 3);
	+ if (count($parts) < 3) {
	+ throw new Exception(
	+ pht(
	+ 'Unexpected output from "hg log ...": %s',
	+ $line));
	+ }
	+
	+ $hash = $parts[0];
	+ if (!isset($commit_map[$hash])) {
	+ $parents = $parts[1];
	+ $parents = trim($parents);
	+ if (strlen($parents)) {
	+ $parents = explode(' ', $parents);
	+ } else {
	+ $parents = array();
	+ }
	+
	+ $summary = $parts[2];
	+
	+ $commit_map[$hash] = id(new ArcanistLandCommit())
	+ ->setHash($hash)
	+ ->setParents($parents)
	+ ->setSummary($summary);
	+ }
	+
	+ $commit = $commit_map[$hash];
	+ $commit->addSymbol($symbol);
	+ }
	+ }
	+
	+ return $this->confirmCommits($into_commit, $symbols, $commit_map);
	+ }
	+
	+ protected function executeMerge(ArcanistLandCommitSet $set, $into_commit) {
	+ $api = $this->getRepositoryAPI();
	+
	+ if ($this->getStrategy() !== 'squash') {
	+ throw new Exception(pht('TODO: Support merge strategies'));
	+ }
	+
	+ // TODO: Add a Mercurial version check requiring 2.1.1 or newer.
	+
	+ $api->execxLocal(
	+ 'update --rev %s',
	+ hgsprintf('%s', $into_commit));
	+
	+ $commits = $set->getCommits();
	+
	+ $min_commit = last($commits)->getHash();
	+ $max_commit = head($commits)->getHash();
	+
	+ $revision_ref = $set->getRevisionRef();
	+ $commit_message = $revision_ref->getCommitMessage();
	+
	+ try {
	+ $argv = array();
	+ $argv[] = '--dest';
	+ $argv[] = hgsprintf('%s', $into_commit);
	+
	+ $argv[] = '--rev';
	+ $argv[] = hgsprintf('%s..%s', $min_commit, $max_commit);
	+
	+ $argv[] = '--logfile';
	+ $argv[] = '-';
	+
	+ $argv[] = '--keep';
	+ $argv[] = '--collapse';
	+
	+ $future = $api->execFutureLocal('rebase %Ls', $argv);
	+ $future->write($commit_message);
	+ $future->resolvex();
	+
	+ } catch (CommandException $ex) {
	+ // TODO
	+ // $api->execManualLocal('rebase --abort');
	+ throw $ex;
	+ }
	+
	+ list($stdout) = $api->execxLocal('log --rev tip --template %s', '{node}');
	+ $new_cursor = trim($stdout);
	+
	+ return $new_cursor;
	+ }
	+
	+ protected function pushChange($into_commit) {
	+ $api = $this->getRepositoryAPI();
	+
	+ // TODO: This does not respect "--into" or "--onto" properly.
	+
	+ $api->execxLocal(
	+ 'push --rev %s -- %s',
	+ $into_commit,
	+ $this->getOntoRemote());
	+ }
	+
	+ protected function cascadeState(ArcanistLandCommitSet $set, $into_commit) {
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ // This has no effect when we're executing a merge strategy.
	+ if (!$this->isSquashStrategy()) {
	+ return;
	+ }
	+
	+ $old_commit = last($set->getCommits())->getHash();
	+ $new_commit = $into_commit;
	+
	+ list($output) = $api->execxLocal(
	+ 'log --rev %s --template %s',
	+ hgsprintf('children(%s)', $old_commit),
	+ '{node}\n');
	+ $child_hashes = phutil_split_lines($output, false);
	+
	+ foreach ($child_hashes as $child_hash) {
	+ if (!strlen($child_hash)) {
	+ continue;
	+ }
	+
	+ // TODO: If the only heads which are descendants of this child will
	+ // be deleted, we can skip this rebase?
	+
	+ try {
	+ $api->execxLocal(
	+ 'rebase --source %s --dest %s --keep --keepbranches',
	+ $child_hash,
	+ $new_commit);
	+ } catch (CommandException $ex) {
	+ // TODO: Recover state.
	+ throw $ex;
	+ }
	+ }
	+ }
	+
	+
	+ protected function pruneBranches(array $sets) {
	+ assert_instances_of($sets, 'ArcanistLandCommitSet');
	+ $api = $this->getRepositoryAPI();
	+ $log = $this->getLogEngine();
	+
	+ // This has no effect when we're executing a merge strategy.
	+ if (!$this->isSquashStrategy()) {
	+ return;
	+ }
	+
	+ $strip = array();
	+
	+ // We've rebased all descendants already, so we can safely delete all
	+ // of these commits.
	+
	+ $sets = array_reverse($sets);
	+ foreach ($sets as $set) {
	+ $commits = $set->getCommits();
	+
	+ $min_commit = head($commits)->getHash();
	+ $max_commit = last($commits)->getHash();
	+
	+ $strip[] = hgsprintf('%s::%s', $min_commit, $max_commit);
	+ }
	+
	+ $rev_set = '('.implode(') or (', $strip).')';
	+
	+ // See PHI45. If we have "hg evolve", get rid of old commits using
	+ // "hg prune" instead of "hg strip".
	+
	+ // If we "hg strip" a commit which has an obsolete predecessor, it
	+ // removes the obsolescence marker and revives the predecessor. This is
	+ // not desirable: we want to destroy all predecessors of these commits.
	+
	+ try {
	+ $api->execxLocal(
	+ '--config extensions.evolve= prune --rev %s',
	+ $rev_set);
	+ } catch (CommandException $ex) {
	+ $api->execxLocal(
	+ '--config extensions.strip= strip --rev %s',
	+ $rev_set);
	+ }
	+ }
	+
	+ protected function reconcileLocalState(
	+ $into_commit,
	+ ArcanistRepositoryLocalState $state) {
	+
	+ // TODO: For now, just leave users wherever they ended up.
	+
	+ $state->discardLocalState();
	+ }
	+
	+}
	diff --git a/src/query/ArcanistMercurialCommitMessageHardpointQuery.php b/src/query/ArcanistMercurialCommitMessageHardpointQuery.php
	new file mode 100644
	--- /dev/null
	+++ b/src/query/ArcanistMercurialCommitMessageHardpointQuery.php
	@@ -0,0 +1,36 @@
	+<?php
	+
	+final class ArcanistMercurialCommitMessageHardpointQuery
	+ extends ArcanistWorkflowMercurialHardpointQuery {
	+
	+ public function getHardpoints() {
	+ return array(
	+ ArcanistCommitRef::HARDPOINT_MESSAGE,
	+ );
	+ }
	+
	+ protected function canLoadRef(ArcanistRef $ref) {
	+ return ($ref instanceof ArcanistCommitRef);
	+ }
	+
	+ public function loadHardpoint(array $refs, $hardpoint) {
	+ $api = $this->getRepositoryAPI();
	+
	+ $hashes = mpull($refs, 'getCommitHash');
	+ $unique_hashes = array_fuse($hashes);
	+
	+ // TODO: Batch this properly and make it future oriented.
	+
	+ $messages = array();
	+ foreach ($unique_hashes as $unique_hash) {
	+ $messages[$unique_hash] = $api->getCommitMessage($unique_hash);
	+ }
	+
	+ foreach ($hashes as $ref_key => $hash) {
	+ $hashes[$ref_key] = $messages[$hash];
	+ }
	+
	+ yield $this->yieldMap($hashes);
	+ }
	+
	+}
	diff --git a/src/query/ArcanistMercurialWorkingCopyRevisionHardpointQuery.php b/src/query/ArcanistMercurialWorkingCopyRevisionHardpointQuery.php
	new file mode 100644
	--- /dev/null
	+++ b/src/query/ArcanistMercurialWorkingCopyRevisionHardpointQuery.php
	@@ -0,0 +1,76 @@
	+<?php
	+
	+final class ArcanistMercurialWorkingCopyRevisionHardpointQuery
	+ extends ArcanistWorkflowMercurialHardpointQuery {
	+
	+ public function getHardpoints() {
	+ return array(
	+ ArcanistWorkingCopyStateRef::HARDPOINT_REVISIONREFS,
	+ );
	+ }
	+
	+ protected function canLoadRef(ArcanistRef $ref) {
	+ return ($ref instanceof ArcanistWorkingCopyStateRef);
	+ }
	+
	+ public function loadHardpoint(array $refs, $hardpoint) {
	+ yield $this->yieldRequests(
	+ $refs,
	+ array(
	+ ArcanistWorkingCopyStateRef::HARDPOINT_COMMITREF,
	+ ));
	+
	+ // TODO: This has a lot in common with the Git query in the same role.
	+
	+ $hashes = array();
	+ $map = array();
	+ foreach ($refs as $ref_key => $ref) {
	+ $commit = $ref->getCommitRef();
	+
	+ $commit_hashes = array();
	+
	+ $commit_hashes[] = array(
	+ 'hgcm',
	+ $commit->getCommitHash(),
	+ );
	+
	+ foreach ($commit_hashes as $hash) {
	+ $hashes[] = $hash;
	+ $hash_key = $this->getHashKey($hash);
	+ $map[$hash_key][$ref_key] = $ref;
	+ }
	+ }
	+
	+ $results = array_fill_keys(array_keys($refs), array());
	+ if ($hashes) {
	+ $revisions = (yield $this->yieldConduit(
	+ 'differential.query',
	+ array(
	+ 'commitHashes' => $hashes,
	+ )));
	+
	+ foreach ($revisions as $dict) {
	+ $revision_hashes = idx($dict, 'hashes');
	+ if (!$revision_hashes) {
	+ continue;
	+ }
	+
	+ $revision_ref = ArcanistRevisionRef::newFromConduitQuery($dict);
	+ foreach ($revision_hashes as $revision_hash) {
	+ $hash_key = $this->getHashKey($revision_hash);
	+ $state_refs = idx($map, $hash_key, array());
	+ foreach ($state_refs as $ref_key => $state_ref) {
	+ $results[$ref_key][] = $revision_ref;
	+ }
	+ }
	+ }
	+ }
	+
	+ yield $this->yieldMap($results);
	+ }
	+
	+ private function getHashKey(array $hash) {
	+ return $hash[0].':'.$hash[1];
	+ }
	+
	+}
	diff --git a/src/query/ArcanistWorkflowMercurialHardpointQuery.php b/src/query/ArcanistWorkflowMercurialHardpointQuery.php
	new file mode 100644
	--- /dev/null
	+++ b/src/query/ArcanistWorkflowMercurialHardpointQuery.php
	@@ -0,0 +1,11 @@
	+<?php
	+
	+abstract class ArcanistWorkflowMercurialHardpointQuery
	+ extends ArcanistRuntimeHardpointQuery {
	+
	+ final protected function canLoadHardpoint() {
	+ $api = $this->getRepositoryAPI();
	+ return ($api instanceof ArcanistMercurialAPI);
	+ }
	+
	+}
	diff --git a/src/ref/revision/ArcanistRevisionBuildableHardpointQuery.php b/src/ref/revision/ArcanistRevisionBuildableHardpointQuery.php
	--- a/src/ref/revision/ArcanistRevisionBuildableHardpointQuery.php
	+++ b/src/ref/revision/ArcanistRevisionBuildableHardpointQuery.php
	@@ -29,7 +29,7 @@
	$buildables = (yield $this->yieldConduitSearch(
	'harbormaster.buildable.search',
	array(
	- 'objectPHIDs' => $diff_map,
	+ 'objectPHIDs' => array_values($diff_map),
	'manual' => false,
	)));

	diff --git a/src/repository/api/ArcanistGitAPI.php b/src/repository/api/ArcanistGitAPI.php
	--- a/src/repository/api/ArcanistGitAPI.php
	+++ b/src/repository/api/ArcanistGitAPI.php
	@@ -1564,6 +1564,11 @@
	return ($uri !== null);
	}

	+ public function isFetchableRemote($remote_name) {
	+ $uri = $this->getGitRemoteFetchURI($remote_name);
	+ return ($uri !== null);
	+ }
	+
	private function getGitRemoteFetchURI($remote_name) {
	return $this->getGitRemoteURI($remote_name, $for_push = false);
	}
	@@ -1739,4 +1744,13 @@
	return false;
	}

	+ protected function newLandEngine() {
	+ return new ArcanistGitLandEngine();
	+ }
	+
	+ public function newLocalState() {
	+ return id(new ArcanistGitLocalState())
	+ ->setRepositoryAPI($this);
	+ }
	+
	}
	diff --git a/src/repository/api/ArcanistMercurialAPI.php b/src/repository/api/ArcanistMercurialAPI.php
	--- a/src/repository/api/ArcanistMercurialAPI.php
	+++ b/src/repository/api/ArcanistMercurialAPI.php
	@@ -534,6 +534,8 @@
	}

	public function getAllBranches() {
	+ // TODO: This is wrong, and returns bookmarks.
	+
	list($branch_info) = $this->execxLocal('bookmarks');
	if (trim($branch_info) == 'no bookmarks set') {
	return array();
	@@ -548,10 +550,14 @@

	$return = array();
	foreach ($matches as $match) {
	- list(, $current, $name) = $match;
	+ list(, $current, $name, $hash) = $match;
	+
	+ list($id, $hash) = explode(':', $hash);
	+
	$return[] = array(
	'current' => (bool)$current,
	'name' => rtrim($name),
	+ 'hash' => $hash,
	);
	}
	return $return;
	@@ -562,9 +568,13 @@

	$refs = array();
	foreach ($branches as $branch) {
	+ $commit_ref = $this->newCommitRef()
	+ ->setCommitHash($branch['hash']);
	+
	$refs[] = $this->newBranchRef()
	->setBranchName($branch['name'])
	- ->setIsCurrentBranch($branch['current']);
	+ ->setIsCurrentBranch($branch['current'])
	+ ->attachCommitRef($commit_ref);
	}

	return $refs;
	@@ -1064,6 +1074,46 @@
	return $bookmarks;
	}

	+ public function getBookmarkCommitHash($name) {
	+ // TODO: Cache this.
	+
	+ $bookmarks = $this->getBookmarks($name);
	+ $bookmarks = ipull($bookmarks, null, 'name');
	+
	+ foreach ($bookmarks as $bookmark) {
	+ if ($bookmark['name'] === $name) {
	+ return $bookmark['revision'];
	+ }
	+ }
	+
	+ throw new Exception(pht('No bookmark "%s".', $name));
	+ }
	+
	+ public function getBranchCommitHash($name) {
	+ // TODO: Cache this.
	+ // TODO: This won't work when there are multiple branch heads with the
	+ // same name.
	+
	+ $branches = $this->getBranches($name);
	+
	+ $heads = array();
	+ foreach ($branches as $branch) {
	+ if ($branch['name'] === $name) {
	+ $heads[] = $branch;
	+ }
	+ }
	+
	+ if (count($heads) === 1) {
	+ return idx(head($heads), 'revision');
	+ }
	+
	+ if (!$heads) {
	+ throw new Exception(pht('No branch "%s".', $name));
	+ }
	+
	+ throw new Exception(pht('Too many branch heads for "%s".', $name));
	+ }
	+
	private function splitBranchOrBookmarkLine($line) {
	// branches and bookmarks are printed in the format:
	// default 0:a5ead76cdf85 (inactive)
	@@ -1108,4 +1158,14 @@
	return $env;
	}

	+ protected function newLandEngine() {
	+ return new ArcanistMercurialLandEngine();
	+ }
	+
	+ public function newLocalState() {
	+ return id(new ArcanistMercurialLocalState())
	+ ->setRepositoryAPI($this);
	+ }
	+
	+
	}
	diff --git a/src/repository/api/ArcanistRepositoryAPI.php b/src/repository/api/ArcanistRepositoryAPI.php
	--- a/src/repository/api/ArcanistRepositoryAPI.php
	+++ b/src/repository/api/ArcanistRepositoryAPI.php
	@@ -734,4 +734,19 @@
	final public function newBranchRef() {
	return new ArcanistBranchRef();
	}
	+
	+ final public function getLandEngine() {
	+ $engine = $this->newLandEngine();
	+
	+ if ($engine) {
	+ $engine->setRepositoryAPI($this);
	+ }
	+
	+ return $engine;
	+ }
	+
	+ protected function newLandEngine() {
	+ return null;
	+ }
	+
	}
	diff --git a/src/repository/state/ArcanistMercurialLocalState.php b/src/repository/state/ArcanistMercurialLocalState.php
	new file mode 100644
	--- /dev/null
	+++ b/src/repository/state/ArcanistMercurialLocalState.php
	@@ -0,0 +1,60 @@
	+<?php
	+
	+final class ArcanistMercurialLocalState
	+ extends ArcanistRepositoryLocalState {
	+
	+ private $localCommit;
	+ private $localRef;
	+ private $localPath;
	+
	+ public function getLocalRef() {
	+ return $this->localRef;
	+ }
	+
	+ public function getLocalPath() {
	+ return $this->localPath;
	+ }
	+
	+ protected function executeSaveLocalState() {
	+ $api = $this->getRepositoryAPI();
	+ // TODO: Fix this.
	+ }
	+
	+ protected function executeRestoreLocalState() {
	+ $api = $this->getRepositoryAPI();
	+ // TODO: Fix this.
	+
	+ // TODO: In Mercurial, we may want to discard commits we've created.
	+ // $repository_api->execxLocal(
	+ // '--config extensions.mq= strip %s',
	+ // $this->onto);
	+
	+ }
	+
	+ protected function executeDiscardLocalState() {
	+ // TODO: Fix this.
	+ }
	+
	+ protected function canStashChanges() {
	+ // Depends on stash extension.
	+ return false;
	+ }
	+
	+ protected function getIgnoreHints() {
	+ // TODO: Provide this.
	+ return array();
	+ }
	+
	+ protected function saveStash() {
	+ return null;
	+ }
	+
	+ protected function restoreStash($stash_ref) {
	+ return null;
	+ }
	+
	+ protected function discardStash($stash_ref) {
	+ return null;
	+ }
	+
	+}
	diff --git a/src/repository/state/ArcanistRepositoryLocalState.php b/src/repository/state/ArcanistRepositoryLocalState.php
	--- a/src/repository/state/ArcanistRepositoryLocalState.php
	+++ b/src/repository/state/ArcanistRepositoryLocalState.php
	@@ -151,6 +151,9 @@
	$this->executeSaveLocalState();
	$this->shouldRestore = true;

	+ // TODO: Detect when we're in the middle of a rebase.
	+ // TODO: Detect when we're in the middle of a cherry-pick.
	+
	return $this;
	}

	diff --git a/src/workflow/ArcanistLandWorkflow.php b/src/workflow/ArcanistLandWorkflow.php
	--- a/src/workflow/ArcanistLandWorkflow.php
	+++ b/src/workflow/ArcanistLandWorkflow.php
	@@ -3,1608 +3,281 @@
	/**
	* Lands a branch by rebasing, merging and amending it.
	*/
	-final class ArcanistLandWorkflow extends ArcanistWorkflow {
	-
	- private $isGit;
	- private $isGitSvn;
	- private $isHg;
	- private $isHgSvn;
	-
	- private $oldBranch;
	- private $branch;
	- private $onto;
	- private $ontoRemoteBranch;
	- private $remote;
	- private $useSquash;
	- private $keepBranch;
	- private $branchType;
	- private $ontoType;
	- private $preview;
	-
	- private $revision;
	- private $messageFile;
	-
	- const REFTYPE_BRANCH = 'branch';
	- const REFTYPE_BOOKMARK = 'bookmark';
	-
	- public function getRevisionDict() {
	- return $this->revision;
	- }
	+final class ArcanistLandWorkflow
	+ extends ArcanistArcWorkflow {

	public function getWorkflowName() {
	return 'land';
	}

	- public function getCommandSynopses() {
	- return phutil_console_format(<<<EOTEXT
	- land [__options__] [__ref__]
	-EOTEXT
	- );
	- }
	-
	- public function getCommandHelp() {
	- return phutil_console_format(<<<EOTEXT
	- Supports: git, git/p4, hg
	+ public function getWorkflowInformation() {
	+ $help = pht(<<<EOTEXT
	+Supports: git, git/p4, hg

	- Publish an accepted revision after review. This command is the last
	- step in the standard Differential code review workflow.
	+Publish an accepted revision after review. This command is the last
	+step in the standard Differential code review workflow.

	- This command merges and pushes changes associated with an accepted
	- revision that are currently sitting in __ref__, which is usually the
	- name of a local branch. Without __ref__, the current working copy
	- state will be used.
	+This command merges and pushes changes associated with an accepted
	+revision that are currently sitting in __ref__, which is usually the
	+name of a local branch. Without __ref__, the current working copy
	+state will be used.

	- Under Git: branches, tags, and arbitrary commits (detached HEADs)
	- may be landed.
	+Under Git: branches, tags, and arbitrary commits (detached HEADs)
	+may be landed.

	- Under Git/Perforce: branches, tags, and arbitrary commits may
	- be submitted.
	+Under Git/Perforce: branches, tags, and arbitrary commits may
	+be submitted.

	- Under Mercurial: branches and bookmarks may be landed, but only
	- onto a target of the same type. See T3855.
	+Under Mercurial: branches and bookmarks may be landed, but only
	+onto a target of the same type. See T3855.

	- The workflow selects a target branch to land onto and a remote where
	- the change will be pushed to.
	+The workflow selects a target branch to land onto and a remote where
	+the change will be pushed to.

	- A target branch is selected by examining these sources in order:
	+A target branch is selected by examining these sources in order:

	- - the --onto flag;
	- - the upstream of the branch targeted by the land operation,
	- recursively (Git only);
	- - the __arc.land.onto.default__ configuration setting;
	- - or by falling back to a standard default:
	- - "master" in Git;
	- - "default" in Mercurial.
	+ - the --onto flag;
	+ - the upstream of the branch targeted by the land operation,
	+ recursively (Git only);
	+ - the __arc.land.onto.default__ configuration setting;
	+ - or by falling back to a standard default:
	+ - "master" in Git;
	+ - "default" in Mercurial.

	- A remote is selected by examining these sources in order:
	+A remote is selected by examining these sources in order:

	- - the --remote flag;
	- - the upstream of the current branch, recursively (Git only);
	- - the special "p4" remote which indicates a repository has
	- been synchronized with Perforce (Git only);
	- - or by falling back to a standard default:
	- - "origin" in Git;
	- - the default remote in Mercurial.
	+ - the --remote flag;
	+ - the upstream of the current branch, recursively (Git only);
	+ - the special "p4" remote which indicates a repository has
	+ been synchronized with Perforce (Git only);
	+ - or by falling back to a standard default:
	+ - "origin" in Git;
	+ - the default remote in Mercurial.

	- After selecting a target branch and a remote, the commits which will
	- be landed are printed.
	+After selecting a target branch and a remote, the commits which will
	+be landed are printed.

	- With --preview, execution stops here, before the change is
	- merged.
	+With --preview, execution stops here, before the change is
	+merged.

	- The change is merged with the changes in the target branch,
	- following these rules:
	+The change is merged with the changes in the target branch,
	+following these rules:

	- In repositories with mutable history or with --squash, this will
	- perform a squash merge (the entire branch will be represented as one
	- commit after the merge).
	+In repositories with mutable history or with --squash, this will
	+perform a squash merge (the entire branch will be represented as one
	+commit after the merge).

	- In repositories with immutable history or with --merge, this will
	- perform a strict merge (a merge commit will always be created, and
	- local commits will be preserved).
	+In repositories with immutable history or with --merge, this will
	+perform a strict merge (a merge commit will always be created, and
	+local commits will be preserved).

	- The resulting commit will be given an up-to-date commit message
	- describing the final state of the revision in Differential.
	+The resulting commit will be given an up-to-date commit message
	+describing the final state of the revision in Differential.

	- In Git, the merge occurs in a detached HEAD. The local branch
	- reference (if one exists) is not updated yet.
	+In Git, the merge occurs in a detached HEAD. The local branch
	+reference (if one exists) is not updated yet.

	- With --hold, execution stops here, before the change is pushed.
	+With --hold, execution stops here, before the change is pushed.

	- The change is pushed into the remote.
	+The change is pushed into the remote.

	- Consulting mystical sources of power, the workflow makes a guess
	- about what state you wanted to end up in after the process finishes
	- and the working copy is put into that state.
	-
	- The branch which was landed is deleted, unless the --keep-branch
	- flag was passed or the landing branch is the same as the target
	- branch.
	+Consulting mystical sources of power, the workflow makes a guess
	+about what state you wanted to end up in after the process finishes
	+and the working copy is put into that state.

	+The branch which was landed is deleted, unless the --keep-branch
	+flag was passed or the landing branch is the same as the target
	+branch.
	EOTEXT
	);
	- }
	-
	- public function requiresWorkingCopy() {
	- return true;
	- }
	-
	- public function requiresConduit() {
	- return true;
	- }

	- public function requiresAuthentication() {
	- return true;
	- }
	+ // TODO: Add command synopses.

	- public function requiresRepositoryAPI() {
	- return true;
	+ return $this->newWorkflowInformation()
	+ ->setHelp($help);
	}

	- public function getArguments() {
	+ public function getWorkflowArguments() {
	return array(
	- 'onto' => array(
	- 'param' => 'master',
	- 'help' => pht(
	- "Land feature branch onto a branch other than the default ".
	- "('master' in git, 'default' in hg). You can change the default ".
	- "by setting '%s' with `%s` or for the entire project in %s.",
	- 'arc.land.onto.default',
	- 'arc set-config',
	- '.arcconfig'),
	- ),
	- 'hold' => array(
	- 'help' => pht(
	- 'Prepare the change to be pushed, but do not actually push it.'),
	- ),
	- 'keep-branch' => array(
	- 'help' => pht(
	- 'Keep the feature branch after pushing changes to the '.
	- 'remote (by default, it is deleted).'),
	- ),
	- 'remote' => array(
	- 'param' => 'origin',
	- 'help' => pht(
	- 'Push to a remote other than the default.'),
	- ),
	- 'merge' => array(
	- 'help' => pht(
	- 'Perform a %s merge, not a %s merge. If the project '.
	- 'is marked as having an immutable history, this is the default '.
	- 'behavior.',
	- '--no-ff',
	- '--squash'),
	- 'supports' => array(
	- 'git',
	- ),
	- 'nosupport' => array(
	- 'hg' => pht(
	- 'Use the %s strategy when landing in mercurial.',
	- '--squash'),
	- ),
	- ),
	- 'squash' => array(
	- 'help' => pht(
	- 'Perform a %s merge, not a %s merge. If the project is '.
	- 'marked as having a mutable history, this is the default behavior.',
	- '--squash',
	- '--no-ff'),
	- 'conflicts' => array(
	- 'merge' => pht(
	- '%s and %s are conflicting merge strategies.',
	- '--merge',
	- '--squash'),
	- ),
	- ),
	- 'delete-remote' => array(
	- 'help' => pht(
	- 'Delete the feature branch in the remote after landing it.'),
	- 'conflicts' => array(
	- 'keep-branch' => true,
	- ),
	- 'supports' => array(
	- 'hg',
	- ),
	- ),
	- 'revision' => array(
	- 'param' => 'id',
	- 'help' => pht(
	- 'Use the message from a specific revision, rather than '.
	- 'inferring the revision based on branch content.'),
	- ),
	- 'preview' => array(
	- 'help' => pht(
	- 'Prints the commits that would be landed. Does not '.
	- 'actually modify or land the commits.'),
	- ),
	- '*' => 'branch',
	+ $this->newWorkflowArgument('hold')
	+ ->setHelp(
	+ pht(
	+ 'Prepare the change to be pushed, but do not actually push it.')),
	+ $this->newWorkflowArgument('keep-branches')
	+ ->setHelp(
	+ pht(
	+ 'Keep local branches around after changes are pushed. By '.
	+ 'default, local branches are deleted after they land.')),
	+ $this->newWorkflowArgument('onto-remote')
	+ ->setParameter('remote-name')
	+ ->setHelp(pht('Push to a remote other than the default.')),
	+
	+ // TODO: Formally allow flags to be bound to related configuration
	+ // for documentation, e.g. "setRelatedConfiguration('arc.land.onto')".
	+
	+ $this->newWorkflowArgument('onto')
	+ ->setParameter('branch-name')
	+ ->setRepeatable(true)
	+ ->setHelp(
	+ pht(
	+ 'After merging, push changes onto a specified branch. '.
	+ 'Specifying this flag multiple times will push multiple '.
	+ 'branches.')),
	+ $this->newWorkflowArgument('strategy')
	+ ->setParameter('strategy-name')
	+ ->setHelp(
	+ pht(
	+ // TODO: Improve this.
	+ 'Merge using a particular strategy.')),
	+ $this->newWorkflowArgument('revision')
	+ ->setParameter('revision-identifier')
	+ ->setHelp(
	+ pht(
	+ 'Land a specific revision, rather than determining the revisions '.
	+ 'from the commits that are landing.')),
	+ $this->newWorkflowArgument('preview')
	+ ->setHelp(
	+ pht(
	+ 'Shows the changes that will land. Does not modify the working '.
	+ 'copy or the remote.')),
	+ $this->newWorkflowArgument('into')
	+ ->setParameter('commit-ref')
	+ ->setHelp(
	+ pht(
	+ 'Specifies the state to merge into. By default, this is the same '.
	+ 'as the "onto" ref.')),
	+ $this->newWorkflowArgument('into-remote')
	+ ->setParameter('remote-name')
	+ ->setHelp(
	+ pht(
	+ 'Specifies the remote to fetch the "into" ref from. By '.
	+ 'default, this is the same as the "onto" remote.')),
	+ $this->newWorkflowArgument('into-local')
	+ ->setHelp(
	+ pht(
	+ 'Use the local "into" ref state instead of fetching it from '.
	+ 'a remote.')),
	+ $this->newWorkflowArgument('into-empty')
	+ ->setHelp(
	+ pht(
	+ 'Merge into the empty state instead of an existing state. This '.
	+ 'mode is primarily useful when creating a new repository, and '.
	+ 'selected automatically if the "onto" ref does not exist and the '.
	+ '"into" state is not specified.')),
	+ $this->newWorkflowArgument('incremental')
	+ ->setHelp(
	+ pht(
	+ 'When landing multiple revisions at once, push and rebase '.
	+ 'after each operation instead of waiting until all merges '.
	+ 'are completed. This is slower than the default behavior and '.
	+ 'not atomic, but may make it easier to resolve conflicts and '.
	+ 'land complicated changes by letting you make progress one '.
	+ 'step at a time.')),
	+ $this->newWorkflowArgument('ref')
	+ ->setWildcard(true),
	);
	}

	- public function run() {
	- $this->readArguments();
	-
	- $engine = null;
	- if ($this->isGit && !$this->isGitSvn) {
	- $engine = new ArcanistGitLandEngine();
	- }
	-
	- if ($engine) {
	- $should_hold = $this->getArgument('hold');
	- $remote_arg = $this->getArgument('remote');
	- $onto_arg = $this->getArgument('onto');
	-
	- $engine
	- ->setWorkflow($this)
	- ->setRepositoryAPI($this->getRepositoryAPI())
	- ->setSourceRef($this->branch)
	- ->setShouldHold($should_hold)
	- ->setShouldKeep($this->keepBranch)
	- ->setShouldSquash($this->useSquash)
	- ->setShouldPreview($this->preview)
	- ->setRemoteArgument($remote_arg)
	- ->setOntoArgument($onto_arg)
	- ->setBuildMessageCallback(array($this, 'buildEngineMessage'));
	-
	- // The goal here is to raise errors with flags early (which is cheap),
	- // before we test if the working copy is clean (which can be slow). This
	- // could probably be structured more cleanly.
	-
	- $engine->parseArguments();
	-
	- // This must be configured or we fail later inside "buildEngineMessage()".
	- // This is less than ideal.
	- $this->ontoRemoteBranch = sprintf(
	- '%s/%s',
	- $engine->getTargetRemote(),
	- $engine->getTargetOnto());
	-
	- $this->requireCleanWorkingCopy();
	- $engine->execute();
	-
	- if (!$should_hold && !$this->preview) {
	- $this->didPush();
	- }
	-
	- return 0;
	- }
	-
	- $this->validate();
	-
	- try {
	- $this->pullFromRemote();
	- } catch (Exception $ex) {
	- $this->restoreBranch();
	- throw $ex;
	- }
	-
	- $this->printPendingCommits();
	- if ($this->preview) {
	- $this->restoreBranch();
	- return 0;
	- }
	-
	- $this->checkoutBranch();
	- $this->findRevision();
	-
	- if ($this->useSquash) {
	- $this->rebase();
	- $this->squash();
	- } else {
	- $this->merge();
	- }
	-
	- $this->push();
	-
	- if (!$this->keepBranch) {
	- $this->cleanupBranch();
	- }
	-
	- if ($this->oldBranch != $this->onto) {
	- // If we were on some branch A and the user ran "arc land B",
	- // switch back to A.
	- if ($this->keepBranch \|\| $this->oldBranch != $this->branch) {
	- $this->restoreBranch();
	- }
	- }
	-
	- echo pht('Done.'), "\n";
	-
	- return 0;
	- }
	-
	- private function getUpstreamMatching($branch, $pattern) {
	- if ($this->isGit) {
	- $repository_api = $this->getRepositoryAPI();
	- list($err, $fullname) = $repository_api->execManualLocal(
	- 'rev-parse --symbolic-full-name %s@{upstream}',
	- $branch);
	- if (!$err) {
	- $matches = null;
	- if (preg_match($pattern, $fullname, $matches)) {
	- return last($matches);
	- }
	- }
	- }
	- return null;
	- }
	-
	- private function getGitSvnTrunk() {
	- if (!$this->isGitSvn) {
	- return null;
	- }
	-
	- // See T13293, this depends on the options passed when cloning.
	- // On any error we return `trunk`, which was the previous default.
	-
	- $repository_api = $this->getRepositoryAPI();
	- list($err, $refspec) = $repository_api->execManualLocal(
	- 'config svn-remote.svn.fetch');
	-
	- if ($err) {
	- return 'trunk';
	- }
	-
	- $refspec = rtrim(substr($refspec, strrpos($refspec, ':') + 1));
	-
	- $prefix = 'refs/remotes/';
	- if (substr($refspec, 0, strlen($prefix)) !== $prefix) {
	- return 'trunk';
	- }
	-
	- $refspec = substr($refspec, strlen($prefix));
	- return $refspec;
	- }
	-
	- private function readArguments() {
	- $repository_api = $this->getRepositoryAPI();
	- $this->isGit = $repository_api instanceof ArcanistGitAPI;
	- $this->isHg = $repository_api instanceof ArcanistMercurialAPI;
	-
	- if ($this->isGit) {
	- $repository = $this->loadProjectRepository();
	- $this->isGitSvn = (idx($repository, 'vcs') == 'svn');
	- }
	-
	- if ($this->isHg) {
	- $this->isHgSvn = $repository_api->isHgSubversionRepo();
	- }
	-
	- $branch = $this->getArgument('branch');
	- if (empty($branch)) {
	- $branch = $this->getBranchOrBookmark();
	- if ($branch !== null) {
	- $this->branchType = $this->getBranchType($branch);
	-
	- // TODO: This message is misleading when landing a detached head or
	- // a tag in Git.
	-
	- echo pht("Landing current %s '%s'.", $this->branchType, $branch), "\n";
	- $branch = array($branch);
	- }
	- }
	-
	- if (count($branch) !== 1) {
	- throw new ArcanistUsageException(
	- pht('Specify exactly one branch or bookmark to land changes from.'));
	- }
	- $this->branch = head($branch);
	- $this->keepBranch = $this->getArgument('keep-branch');
	-
	- $this->preview = $this->getArgument('preview');
	-
	- if (!$this->branchType) {
	- $this->branchType = $this->getBranchType($this->branch);
	- }
	-
	- $onto_default = $this->isGit ? 'master' : 'default';
	- $onto_default = nonempty(
	- $this->getConfigFromAnySource('arc.land.onto.default'),
	- $onto_default);
	- $onto_default = coalesce(
	- $this->getUpstreamMatching($this->branch, '/^refs\/heads\/(.+)$/'),
	- $onto_default);
	- $this->onto = $this->getArgument('onto', $onto_default);
	- $this->ontoType = $this->getBranchType($this->onto);
	-
	- $remote_default = $this->isGit ? 'origin' : '';
	- $remote_default = coalesce(
	- $this->getUpstreamMatching($this->onto, '/^refs\/remotes\/(.+?)\//'),
	- $remote_default);
	- $this->remote = $this->getArgument('remote', $remote_default);
	-
	- if ($this->getArgument('merge')) {
	- $this->useSquash = false;
	- } else if ($this->getArgument('squash')) {
	- $this->useSquash = true;
	- } else {
	- $this->useSquash = !$this->isHistoryImmutable();
	- }
	-
	- $this->ontoRemoteBranch = $this->onto;
	- if ($this->isGitSvn) {
	- $this->ontoRemoteBranch = $this->getGitSvnTrunk();
	- } else if ($this->isGit) {
	- $this->ontoRemoteBranch = $this->remote.'/'.$this->onto;
	- }
	-
	- $this->oldBranch = $this->getBranchOrBookmark();
	- }
	-
	- private function validate() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- if ($this->onto == $this->branch) {
	- $message = pht(
	- "You can not land a %s onto itself -- you are trying ".
	- "to land '%s' onto '%s'. For more information on how to push ".
	- "changes, see 'Pushing and Closing Revisions' in 'Arcanist User ".
	- "Guide: arc diff' in the documentation.",
	- $this->branchType,
	- $this->branch,
	- $this->onto);
	- if (!$this->isHistoryImmutable()) {
	- $message .= ' '.pht("You may be able to '%s' instead.", 'arc amend');
	- }
	- throw new ArcanistUsageException($message);
	- }
	-
	- if ($this->isHg) {
	- if ($this->useSquash) {
	- if (!$repository_api->supportsRebase()) {
	- throw new ArcanistUsageException(
	- pht(
	- 'You must enable the rebase extension to use the %s strategy.',
	- '--squash'));
	- }
	- }
	-
	- if ($this->branchType != $this->ontoType) {
	- throw new ArcanistUsageException(pht(
	- 'Source %s is a %s but destination %s is a %s. When landing a '.
	- '%s, the destination must also be a %s. Use %s to specify a %s, '.
	- 'or set %s in %s.',
	- $this->branch,
	- $this->branchType,
	- $this->onto,
	- $this->ontoType,
	- $this->branchType,
	- $this->branchType,
	- '--onto',
	- $this->branchType,
	- 'arc.land.onto.default',
	- '.arcconfig'));
	- }
	- }
	-
	- if ($this->isGit) {
	- list($err) = $repository_api->execManualLocal(
	- 'rev-parse --verify %s',
	- $this->branch);
	-
	- if ($err) {
	- throw new ArcanistUsageException(
	- pht("Branch '%s' does not exist.", $this->branch));
	- }
	- }
	-
	- $this->requireCleanWorkingCopy();
	- }
	-
	- private function checkoutBranch() {
	- $repository_api = $this->getRepositoryAPI();
	- if ($this->getBranchOrBookmark() != $this->branch) {
	- $repository_api->execxLocal('checkout %s', $this->branch);
	- }
	-
	- switch ($this->branchType) {
	- case self::REFTYPE_BOOKMARK:
	- $message = pht(
	- 'Switched to bookmark %s. Identifying and merging...',
	- $this->branch);
	- break;
	- case self::REFTYPE_BRANCH:
	- default:
	- $message = pht(
	- 'Switched to branch %s. Identifying and merging...',
	- $this->branch);
	- break;
	- }
	-
	- echo phutil_console_format($message."\n");
	- }
	-
	- private function printPendingCommits() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- if ($repository_api instanceof ArcanistGitAPI) {
	- list($out) = $repository_api->execxLocal(
	- 'log --oneline %s %s --',
	- $this->branch,
	- '^'.$this->onto);
	- } else if ($repository_api instanceof ArcanistMercurialAPI) {
	- $common_ancestor = $repository_api->getCanonicalRevisionName(
	- hgsprintf('ancestor(%s,%s)',
	- $this->onto,
	- $this->branch));
	-
	- $branch_range = hgsprintf(
	- 'reverse((%s::%s) - %s)',
	- $common_ancestor,
	- $this->branch,
	- $common_ancestor);
	-
	- list($out) = $repository_api->execxLocal(
	- 'log -r %s --template %s',
	- $branch_range,
	- '{node\|short} {desc\|firstline}\n');
	- }
	-
	- if (!trim($out)) {
	- $this->restoreBranch();
	- throw new ArcanistUsageException(
	- pht('No commits to land from %s.', $this->branch));
	- }
	-
	- echo pht("The following commit(s) will be landed:\n\n%s", $out), "\n";
	- }
	-
	- private function findRevision() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- $this->parseBaseCommitArgument(array($this->ontoRemoteBranch));
	-
	- $revision_id = $this->getArgument('revision');
	- if ($revision_id) {
	- $revision_id = $this->normalizeRevisionID($revision_id);
	- $revisions = $this->getConduit()->callMethodSynchronous(
	- 'differential.query',
	- array(
	- 'ids' => array($revision_id),
	- ));
	- if (!$revisions) {
	- throw new ArcanistUsageException(pht(
	- "No such revision '%s'!",
	- "D{$revision_id}"));
	- }
	- } else {
	- $revisions = $repository_api->loadWorkingCopyDifferentialRevisions(
	- $this->getConduit(),
	- array());
	- }
	-
	- if (!count($revisions)) {
	- throw new ArcanistUsageException(pht(
	- "arc can not identify which revision exists on %s '%s'. Update the ".
	- "revision with recent changes to synchronize the %s name and hashes, ".
	- "or use '%s' to amend the commit message at HEAD, or use ".
	- "'%s' to select a revision explicitly.",
	- $this->branchType,
	- $this->branch,
	- $this->branchType,
	- 'arc amend',
	- '--revision <id>'));
	- } else if (count($revisions) > 1) {
	- switch ($this->branchType) {
	- case self::REFTYPE_BOOKMARK:
	- $message = pht(
	- "There are multiple revisions on feature bookmark '%s' which are ".
	- "not present on '%s':\n\n".
	- "%s\n".
	- 'Separate these revisions onto different bookmarks, or use '.
	- '--revision <id> to use the commit message from <id> '.
	- 'and land them all.',
	- $this->branch,
	- $this->onto,
	- $this->renderRevisionList($revisions));
	- break;
	- case self::REFTYPE_BRANCH:
	- default:
	- $message = pht(
	- "There are multiple revisions on feature branch '%s' which are ".
	- "not present on '%s':\n\n".
	- "%s\n".
	- 'Separate these revisions onto different branches, or use '.
	- '--revision <id> to use the commit message from <id> '.
	- 'and land them all.',
	- $this->branch,
	- $this->onto,
	- $this->renderRevisionList($revisions));
	- break;
	- }
	-
	- throw new ArcanistUsageException($message);
	- }
	-
	- $this->revision = head($revisions);
	-
	- $rev_status = $this->revision['status'];
	- $rev_id = $this->revision['id'];
	- $rev_title = $this->revision['title'];
	- $rev_auxiliary = idx($this->revision, 'auxiliary', array());
	-
	- $full_name = pht('D%d: %s', $rev_id, $rev_title);
	-
	- if ($this->revision['authorPHID'] != $this->getUserPHID()) {
	- $other_author = $this->getConduit()->callMethodSynchronous(
	- 'user.query',
	- array(
	- 'phids' => array($this->revision['authorPHID']),
	- ));
	- $other_author = ipull($other_author, 'userName', 'phid');
	- $other_author = $other_author[$this->revision['authorPHID']];
	- $ok = phutil_console_confirm(pht(
	- "This %s has revision '%s' but you are not the author. Land this ".
	- "revision by %s?",
	- $this->branchType,
	- $full_name,
	- $other_author));
	- if (!$ok) {
	- throw new ArcanistUserAbortException();
	- }
	- }
	-
	- $state_warning = null;
	- $state_header = null;
	- if ($rev_status == ArcanistDifferentialRevisionStatus::CHANGES_PLANNED) {
	- $state_header = pht('REVISION HAS CHANGES PLANNED');
	- $state_warning = pht(
	- 'The revision you are landing ("%s") is currently in the "%s" state, '.
	- 'indicating that you expect to revise it before moving forward.'.
	- "\n\n".
	- 'Normally, you should resubmit it for review and wait until it is '.
	- '"%s" by reviewers before you continue.'.
	- "\n\n".
	- 'To resubmit the revision for review, either: update the revision '.
	- 'with revised changes; or use "Request Review" from the web interface.',
	- $full_name,
	- pht('Changes Planned'),
	- pht('Accepted'));
	- } else if ($rev_status != ArcanistDifferentialRevisionStatus::ACCEPTED) {
	- $state_header = pht('REVISION HAS NOT BEEN ACCEPTED');
	- $state_warning = pht(
	- 'The revision you are landing ("%s") has not been "%s" by reviewers.',
	- $full_name,
	- pht('Accepted'));
	- }
	-
	- if ($state_warning !== null) {
	- $prompt = pht('Land revision in the wrong state?');
	-
	- id(new PhutilConsoleBlock())
	- ->addParagraph(tsprintf('<bg:yellow> %s </bg>', $state_header))
	- ->addParagraph(tsprintf('%B', $state_warning))
	- ->draw();
	-
	- $ok = phutil_console_confirm($prompt);
	- if (!$ok) {
	- throw new ArcanistUserAbortException();
	- }
	- }
	-
	- if ($rev_auxiliary) {
	- $phids = idx($rev_auxiliary, 'phabricator:depends-on', array());
	- if ($phids) {
	- $dep_on_revs = $this->getConduit()->callMethodSynchronous(
	- 'differential.query',
	- array(
	- 'phids' => $phids,
	- 'status' => 'status-open',
	- ));
	-
	- $open_dep_revs = array();
	- foreach ($dep_on_revs as $dep_on_rev) {
	- $dep_on_rev_id = $dep_on_rev['id'];
	- $dep_on_rev_title = $dep_on_rev['title'];
	- $dep_on_rev_status = $dep_on_rev['status'];
	- $open_dep_revs[$dep_on_rev_id] = $dep_on_rev_title;
	- }
	-
	- if (!empty($open_dep_revs)) {
	- $open_revs = array();
	- foreach ($open_dep_revs as $id => $title) {
	- $open_revs[] = ' - D'.$id.': '.$title;
	- }
	- $open_revs = implode("\n", $open_revs);
	-
	- echo pht(
	- "Revision '%s' depends on open revisions:\n\n%s",
	- "D{$rev_id}: {$rev_title}",
	- $open_revs);
	-
	- $ok = phutil_console_confirm(pht('Continue anyway?'));
	- if (!$ok) {
	- throw new ArcanistUserAbortException();
	- }
	- }
	- }
	- }
	-
	- $message = $this->getConduit()->callMethodSynchronous(
	- 'differential.getcommitmessage',
	- array(
	- 'revision_id' => $rev_id,
	- ));
	-
	- $this->messageFile = new TempFile();
	- Filesystem::writeFile($this->messageFile, $message);
	-
	- echo pht(
	- "Landing revision '%s'...",
	- "D{$rev_id}: {$rev_title}")."\n";
	-
	- $diff_phid = idx($this->revision, 'activeDiffPHID');
	- if ($diff_phid) {
	- $this->checkForBuildables($diff_phid);
	- }
	- }
	-
	- private function pullFromRemote() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- $local_ahead_of_remote = false;
	- if ($this->isGit) {
	- $repository_api->execxLocal('checkout %s', $this->onto);
	-
	- echo phutil_console_format(pht(
	- "Switched to branch %s. Updating branch...\n",
	- $this->onto));
	-
	- try {
	- $repository_api->execxLocal('pull --ff-only --no-stat');
	- } catch (CommandException $ex) {
	- if (!$this->isGitSvn) {
	- throw $ex;
	- }
	- }
	- list($out) = $repository_api->execxLocal(
	- 'log %s..%s',
	- $this->ontoRemoteBranch,
	- $this->onto);
	- if (strlen(trim($out))) {
	- $local_ahead_of_remote = true;
	- } else if ($this->isGitSvn) {
	- $repository_api->execxLocal('svn rebase');
	- }
	-
	- } else if ($this->isHg) {
	- echo phutil_console_format(pht('Updating %s...', $this->onto)."\n");
	-
	- try {
	- list($out, $err) = $repository_api->execxLocal('pull');
	-
	- $divergedbookmark = $this->onto.'@'.$repository_api->getBranchName();
	- if (strpos($err, $divergedbookmark) !== false) {
	- throw new ArcanistUsageException(phutil_console_format(pht(
	- "Local bookmark %s has diverged from the server's %s ".
	- "(now labeled %s). Please resolve this divergence and run ".
	- "'%s' again.",
	- $this->onto,
	- $this->onto,
	- $divergedbookmark,
	- 'arc land')));
	- }
	- } catch (CommandException $ex) {
	- $err = $ex->getError();
	- $stdout = $ex->getStdout();
	-
	- // Copied from: PhabricatorRepositoryPullLocalDaemon.php
	- // NOTE: Between versions 2.1 and 2.1.1, Mercurial changed the
	- // behavior of "hg pull" to return 1 in case of a successful pull
	- // with no changes. This behavior has been reverted, but users who
	- // updated between Feb 1, 2012 and Mar 1, 2012 will have the
	- // erroring version. Do a dumb test against stdout to check for this
	- // possibility.
	- // See: https://github.com/phacility/phabricator/issues/101/
	-
	- // NOTE: Mercurial has translated versions, which translate this error
	- // string. In a translated version, the string will be something else,
	- // like "aucun changement trouve". There didn't seem to be an easy way
	- // to handle this (there are hard ways but this is not a common
	- // problem and only creates log spam, not application failures).
	- // Assume English.
	-
	- // TODO: Remove this once we're far enough in the future that
	- // deployment of 2.1 is exceedingly rare?
	- if ($err != 1 \|\| !preg_match('/no changes found/', $stdout)) {
	- throw $ex;
	- }
	- }
	-
	- // Pull succeeded. Now make sure master is not on an outgoing change
	- if ($repository_api->supportsPhases()) {
	- list($out) = $repository_api->execxLocal(
	- 'log -r %s --template %s', $this->onto, '{phase}');
	- if ($out != 'public') {
	- $local_ahead_of_remote = true;
	- }
	- } else {
	- // execManual instead of execx because outgoing returns
	- // code 1 when there is nothing outgoing
	- list($err, $out) = $repository_api->execManualLocal(
	- 'outgoing -r %s',
	- $this->onto);
	-
	- // $err === 0 means something is outgoing
	- if ($err === 0) {
	- $local_ahead_of_remote = true;
	- }
	- }
	- }
	-
	- if ($local_ahead_of_remote) {
	- throw new ArcanistUsageException(pht(
	- "Local %s '%s' is ahead of remote %s '%s', so landing a feature ".
	- "%s would push additional changes. Push or reset the changes in '%s' ".
	- "before running '%s'.",
	- $this->ontoType,
	- $this->onto,
	- $this->ontoType,
	- $this->ontoRemoteBranch,
	- $this->ontoType,
	- $this->onto,
	- 'arc land'));
	- }
	- }
	-
	- private function rebase() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- chdir($repository_api->getPath());
	- if ($this->isHg) {
	- $onto_tip = $repository_api->getCanonicalRevisionName($this->onto);
	- $common_ancestor = $repository_api->getCanonicalRevisionName(
	- hgsprintf('ancestor(%s, %s)', $this->onto, $this->branch));
	-
	- // Only rebase if the local branch is not at the tip of the onto branch.
	- if ($onto_tip != $common_ancestor) {
	- // keep branch here so later we can decide whether to remove it
	- $err = $repository_api->execPassthru(
	- 'rebase -d %s --keepbranches',
	- $this->onto);
	- if ($err) {
	- echo phutil_console_format("%s\n", pht('Aborting rebase'));
	- $repository_api->execManualLocal('rebase --abort');
	- $this->restoreBranch();
	- throw new ArcanistUsageException(pht(
	- "'%s' failed and the rebase was aborted. This is most ".
	- "likely due to conflicts. Manually rebase %s onto %s, resolve ".
	- "the conflicts, then run '%s' again.",
	- sprintf('hg rebase %s', $this->onto),
	- $this->branch,
	- $this->onto,
	- 'arc land'));
	- }
	- }
	- }
	-
	- $repository_api->reloadWorkingCopy();
	- }
	-
	- private function squash() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- if ($this->isGit) {
	- $repository_api->execxLocal('checkout %s', $this->onto);
	- $repository_api->execxLocal(
	- 'merge --no-stat --squash --ff-only %s',
	- $this->branch);
	- } else if ($this->isHg) {
	- // The hg code is a little more complex than git's because we
	- // need to handle the case where the landing branch has child branches:
	- // -a--------b master
	- // \
	- // w--x mybranch
	- // \--y subbranch1
	- // \--z subbranch2
	- //
	- // arc land --branch mybranch --onto master :
	- // -a--b--wx master
	- // \--y subbranch1
	- // \--z subbranch2
	-
	- $branch_rev_id = $repository_api->getCanonicalRevisionName($this->branch);
	-
	- // At this point $this->onto has been pulled from remote and
	- // $this->branch has been rebased on top of onto(by the rebase()
	- // function). So we're guaranteed to have onto as an ancestor of branch
	- // when we use first((onto::branch)-onto) below.
	- $branch_root = $repository_api->getCanonicalRevisionName(
	- hgsprintf('first((%s::%s)-%s)',
	- $this->onto,
	- $this->branch,
	- $this->onto));
	-
	- $branch_range = hgsprintf(
	- '(%s::%s)',
	- $branch_root,
	- $this->branch);
	-
	- if (!$this->keepBranch) {
	- $this->handleAlternateBranches($branch_root, $branch_range);
	- }
	-
	- // Collapse just the landing branch onto master.
	- // Leave its children on the original branch.
	- $err = $repository_api->execPassthru(
	- 'rebase --collapse --keep --logfile %s -r %s -d %s',
	- $this->messageFile,
	- $branch_range,
	- $this->onto);
	-
	- if ($err) {
	- $repository_api->execManualLocal('rebase --abort');
	- $this->restoreBranch();
	- throw new ArcanistUsageException(
	+ protected function newPrompts() {
	+ return array(
	+ $this->newPrompt('arc.land.large-working-set')
	+ ->setDescription(
	pht(
	- "Squashing the commits under %s failed. ".
	- "Manually squash your commits and run '%s' again.",
	- $this->branch,
	- 'arc land'));
	- }
	-
	- if ($repository_api->isBookmark($this->branch)) {
	- // a bug in mercurial means bookmarks end up on the revision prior
	- // to the collapse when using --collapse with --keep,
	- // so we manually move them to the correct spots
	- // see: http://bz.selenic.com/show_bug.cgi?id=3716
	- $repository_api->execxLocal(
	- 'bookmark -f %s',
	- $this->onto);
	-
	- $repository_api->execxLocal(
	- 'bookmark -f %s -r %s',
	- $this->branch,
	- $branch_rev_id);
	- }
	-
	- // check if the branch had children
	- list($output) = $repository_api->execxLocal(
	- 'log -r %s --template %s',
	- hgsprintf('children(%s)', $this->branch),
	- '{node}\n');
	-
	- $child_branch_roots = phutil_split_lines($output, false);
	- $child_branch_roots = array_filter($child_branch_roots);
	- if ($child_branch_roots) {
	- // move the branch's children onto the collapsed commit
	- foreach ($child_branch_roots as $child_root) {
	- $repository_api->execxLocal(
	- 'rebase -d %s -s %s --keep --keepbranches',
	- $this->onto,
	- $child_root);
	- }
	- }
	-
	- // All the rebases may have moved us to another branch
	- // so we move back.
	- $repository_api->execxLocal('checkout %s', $this->onto);
	- }
	- }
	-
	- /**
	- * Detect alternate branches and prompt the user for how to handle
	- * them. An alternate branch is a branch that forks from the landing
	- * branch prior to the landing branch tip.
	- *
	- * In a situation like this:
	- * -a--------b master
	- * \
	- * w--x landingbranch
	- * \ \-- g subbranch
	- * \--y altbranch1
	- * \--z altbranch2
	- *
	- * y and z are alternate branches and will get deleted by the squash,
	- * so we need to detect them and ask the user what they want to do.
	- *
	- * @param string The revision id of the landing branch's root commit.
	- * @param string The revset specifying all the commits in the landing branch.
	- * @return void
	- */
	- private function handleAlternateBranches($branch_root, $branch_range) {
	- $repository_api = $this->getRepositoryAPI();
	-
	- // Using the tree in the doccomment, the revset below resolves as follows:
	- // 1. roots(descendants(w) - descendants(x) - (w::x))
	- // 2. roots({x,g,y,z} - {g} - {w,x})
	- // 3. roots({y,z})
	- // 4. {y,z}
	- $alt_branch_revset = hgsprintf(
	- 'roots(descendants(%s)-descendants(%s)-%R)',
	- $branch_root,
	- $this->branch,
	- $branch_range);
	- list($alt_branches) = $repository_api->execxLocal(
	- 'log --template %s -r %s',
	- '{node}\n',
	- $alt_branch_revset);
	-
	- $alt_branches = phutil_split_lines($alt_branches, false);
	- $alt_branches = array_filter($alt_branches);
	-
	- $alt_count = count($alt_branches);
	- if ($alt_count > 0) {
	- $input = phutil_console_prompt(pht(
	- "%s '%s' has %s %s(s) forking off of it that would be deleted ".
	- "during a squash. Would you like to keep a non-squashed copy, rebase ".
	- "them on top of '%s', or abort and deal with them yourself? ".
	- "(k)eep, (r)ebase, (a)bort:",
	- ucfirst($this->branchType),
	- $this->branch,
	- $alt_count,
	- $this->branchType,
	- $this->branch));
	-
	- if ($input == 'k' \|\| $input == 'keep') {
	- $this->keepBranch = true;
	- } else if ($input == 'r' \|\| $input == 'rebase') {
	- foreach ($alt_branches as $alt_branch) {
	- $repository_api->execxLocal(
	- 'rebase --keep --keepbranches -d %s -s %s',
	- $this->branch,
	- $alt_branch);
	- }
	- } else if ($input == 'a' \|\| $input == 'abort') {
	- $branch_string = implode("\n", $alt_branches);
	- echo
	- "\n",
	+ 'Confirms landing more than %s commit(s) in a single operation.',
	+ new PhutilNumber($this->getLargeWorkingSetLimit()))),
	+ $this->newPrompt('arc.land.confirm')
	+ ->setDescription(
	pht(
	- "Remove the %s starting at these revisions and run %s again:\n%s",
	- $this->branchType.'s',
	- $branch_string,
	- 'arc land'),
	- "\n\n";
	- throw new ArcanistUserAbortException();
	- } else {
	- throw new ArcanistUsageException(
	- pht('Invalid choice. Aborting arc land.'));
	- }
	- }
	- }
	-
	- private function merge() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- // In immutable histories, do a --no-ff merge to force a merge commit with
	- // the right message.
	- $repository_api->execxLocal('checkout %s', $this->onto);
	-
	- chdir($repository_api->getPath());
	- if ($this->isGit) {
	- $err = phutil_passthru(
	- 'git merge --no-stat --no-ff --no-commit %s',
	- $this->branch);
	-
	- if ($err) {
	- throw new ArcanistUsageException(pht(
	- "'%s' failed. Your working copy has been left in a partially ".
	- "merged state. You can: abort with '%s'; or follow the ".
	- "instructions to complete the merge.",
	- 'git merge',
	- 'git merge --abort'));
	- }
	- } else if ($this->isHg) {
	- // HG arc land currently doesn't support --merge.
	- // When merging a bookmark branch to a master branch that
	- // hasn't changed since the fork, mercurial fails to merge.
	- // Instead of only working in some cases, we just disable --merge
	- // until there is a demand for it.
	- // The user should never reach this line, since --merge is
	- // forbidden at the command line argument level.
	- throw new ArcanistUsageException(
	- pht('%s is not currently supported for hg repos.', '--merge'));
	- }
	- }
	-
	- private function push() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- // These commands can fail legitimately (e.g. commit hooks)
	- try {
	- if ($this->isGit) {
	- $repository_api->execxLocal('commit -F %s', $this->messageFile);
	- if (phutil_is_windows()) {
	- // Occasionally on large repositories on Windows, Git can exit with
	- // an unclean working copy here. This prevents reverts from being
	- // pushed to the remote when this occurs.
	- $this->requireCleanWorkingCopy();
	- }
	- } else if ($this->isHg) {
	- // hg rebase produces a commit earlier as part of rebase
	- if (!$this->useSquash) {
	- $repository_api->execxLocal(
	- 'commit --logfile %s',
	- $this->messageFile);
	- }
	- }
	- // We dispatch this event so we can run checks on the merged revision,
	- // right before it gets pushed out. It's easier to do this in arc land
	- // than to try to hook into git/hg.
	- $this->didCommitMerge();
	- } catch (Exception $ex) {
	- $this->executeCleanupAfterFailedPush();
	- throw $ex;
	- }
	-
	- if ($this->getArgument('hold')) {
	- echo phutil_console_format(pht(
	- 'Holding change in %s: it has NOT been pushed yet.',
	- $this->onto)."\n");
	- } else {
	- echo pht('Pushing change...'), "\n\n";
	-
	- chdir($repository_api->getPath());
	-
	- if ($this->isGitSvn) {
	- $err = phutil_passthru('git svn dcommit');
	- $cmd = 'git svn dcommit';
	- } else if ($this->isGit) {
	- $err = phutil_passthru('git push %s %s', $this->remote, $this->onto);
	- $cmd = 'git push';
	- } else if ($this->isHgSvn) {
	- // hg-svn doesn't support 'push -r', so we do a normal push
	- // which hg-svn modifies to only push the current branch and
	- // ancestors.
	- $err = $repository_api->execPassthru('push %s', $this->remote);
	- $cmd = 'hg push';
	- } else if ($this->isHg) {
	- if (strlen($this->remote)) {
	- $err = $repository_api->execPassthru(
	- 'push -r %s %s',
	- $this->onto,
	- $this->remote);
	- } else {
	- $err = $repository_api->execPassthru(
	- 'push -r %s',
	- $this->onto);
	- }
	- $cmd = 'hg push';
	- }
	-
	- if ($err) {
	- echo phutil_console_format(
	- "<bg:red> %s </bg>\n",
	- pht('PUSH FAILED!'));
	- $this->executeCleanupAfterFailedPush();
	- if ($this->isGit) {
	- throw new ArcanistUsageException(pht(
	- "'%s' failed! Fix the error and run '%s' again.",
	- $cmd,
	- 'arc land'));
	- }
	- throw new ArcanistUsageException(pht(
	- "'%s' failed! Fix the error and push this change manually.",
	- $cmd));
	- }
	-
	- $this->didPush();
	-
	- echo "\n";
	- }
	- }
	-
	- private function executeCleanupAfterFailedPush() {
	- $repository_api = $this->getRepositoryAPI();
	- if ($this->isGit) {
	- $repository_api->execxLocal('reset --hard HEAD^');
	- $this->restoreBranch();
	- } else if ($this->isHg) {
	- $repository_api->execxLocal(
	- '--config extensions.mq= strip %s',
	- $this->onto);
	- $this->restoreBranch();
	- }
	- }
	-
	- private function cleanupBranch() {
	- $repository_api = $this->getRepositoryAPI();
	-
	- echo pht('Cleaning up feature %s...', $this->branchType), "\n";
	- if ($this->isGit) {
	- list($ref) = $repository_api->execxLocal(
	- 'rev-parse --verify %s',
	- $this->branch);
	- $ref = trim($ref);
	- $recovery_command = csprintf(
	- 'git checkout -b %s %s',
	- $this->branch,
	- $ref);
	- echo pht('(Use `%s` if you want it back.)', $recovery_command), "\n";
	- $repository_api->execxLocal('branch -D %s', $this->branch);
	- } else if ($this->isHg) {
	- $common_ancestor = $repository_api->getCanonicalRevisionName(
	- hgsprintf('ancestor(%s,%s)', $this->onto, $this->branch));
	-
	- $branch_root = $repository_api->getCanonicalRevisionName(
	- hgsprintf('first((%s::%s)-%s)',
	- $common_ancestor,
	- $this->branch,
	- $common_ancestor));
	-
	- $repository_api->execxLocal(
	- '--config extensions.mq= strip -r %s',
	- $branch_root);
	-
	- if ($repository_api->isBookmark($this->branch)) {
	- $repository_api->execxLocal('bookmark -d %s', $this->branch);
	- }
	- }
	-
	- if ($this->getArgument('delete-remote')) {
	- if ($this->isHg) {
	- // named branches were closed as part of the earlier commit
	- // so only worry about bookmarks
	- if ($repository_api->isBookmark($this->branch)) {
	- $repository_api->execxLocal(
	- 'push -B %s %s',
	- $this->branch,
	- $this->remote);
	- }
	- }
	- }
	- }
	-
	- public function getSupportedRevisionControlSystems() {
	- return array('git', 'hg');
	- }
	-
	- private function getBranchOrBookmark() {
	- $repository_api = $this->getRepositoryAPI();
	- if ($this->isGit) {
	- $branch = $repository_api->getBranchName();
	-
	- // If we don't have a branch name, just use whatever's at HEAD.
	- if (!strlen($branch) && !$this->isGitSvn) {
	- $branch = $repository_api->getWorkingCopyRevision();
	- }
	- } else if ($this->isHg) {
	- $branch = $repository_api->getActiveBookmark();
	- if (!$branch) {
	- $branch = $repository_api->getBranchName();
	- }
	- }
	-
	- return $branch;
	- }
	-
	- private function getBranchType($branch) {
	- $repository_api = $this->getRepositoryAPI();
	- if ($this->isHg && $repository_api->isBookmark($branch)) {
	- return 'bookmark';
	- }
	- return 'branch';
	- }
	-
	- /**
	- * Restore the original branch, e.g. after a successful land or a failed
	- * pull.
	- */
	- private function restoreBranch() {
	- $repository_api = $this->getRepositoryAPI();
	- $repository_api->execxLocal('checkout %s', $this->oldBranch);
	- if ($this->isGit) {
	- $repository_api->execxLocal('submodule update --init --recursive');
	- }
	- echo pht(
	- "Switched back to %s %s.\n",
	- $this->branchType,
	- phutil_console_format('%s', $this->oldBranch));
	+ 'Confirms that the correct changes have been selected.')),
	+ $this->newPrompt('arc.land.implicit')
	+ ->setDescription(
	+ pht(
	+ 'Confirms that local commits which are not associated with '.
	+ 'a revision should land.')),
	+ $this->newPrompt('arc.land.unauthored')
	+ ->setDescription(
	+ pht(
	+ 'Confirms that revisions you did not author should land.')),
	+ $this->newPrompt('arc.land.changes-planned')
	+ ->setDescription(
	+ pht(
	+ 'Confirms that revisions with changes planned should land.')),
	+ $this->newPrompt('arc.land.closed')
	+ ->setDescription(
	+ pht(
	+ 'Confirms that revisions that are already closed should land.')),
	+ $this->newPrompt('arc.land.not-accepted')
	+ ->setDescription(
	+ pht(
	+ 'Confirms that revisions that are not accepted should land.')),
	+ $this->newPrompt('arc.land.open-parents')
	+ ->setDescription(
	+ pht(
	+ 'Confirms that revisions with open parent revisions should '.
	+ 'land.')),
	+ $this->newPrompt('arc.land.failed-builds')
	+ ->setDescription(
	+ pht(
	+ 'Confirms that revisions with failed builds.')),
	+ $this->newPrompt('arc.land.ongoing-builds')
	+ ->setDescription(
	+ pht(
	+ 'Confirms that revisions with ongoing builds.')),
	+ );
	}

	-
	- /**
	- * Check if a diff has a running or failed buildable, and prompt the user
	- * before landing if it does.
	- */
	- private function checkForBuildables($diff_phid) {
	- // Try to use the more modern check which respects the "Warn on Land"
	- // behavioral flag on build plans if we can. This newer check won't work
	- // unless the server is running code from March 2019 or newer since the
	- // API methods we need won't exist yet. We'll fall back to the older check
	- // if this one doesn't work out.
	- try {
	- $this->checkForBuildablesWithPlanBehaviors($diff_phid);
	- return;
	- } catch (ArcanistUserAbortException $abort_ex) {
	- throw $abort_ex;
	- } catch (Exception $ex) {
	- // Continue with the older approach, below.
	- }
	-
	- // NOTE: Since Harbormaster is still beta and this stuff all got added
	- // recently, just bail if we can't find a buildable. This is just an
	- // advisory check intended to prevent human error.
	-
	- try {
	- $buildables = $this->getConduit()->callMethodSynchronous(
	- 'harbormaster.querybuildables',
	- array(
	- 'buildablePHIDs' => array($diff_phid),
	- 'manualBuildables' => false,
	- ));
	- } catch (ConduitClientException $ex) {
	- return;
	- }
	-
	- if (!$buildables['data']) {
	- // If there's no corresponding buildable, we're done.
	- return;
	- }
	-
	- $console = PhutilConsole::getConsole();
	-
	- $buildable = head($buildables['data']);
	-
	- if ($buildable['buildableStatus'] == 'passed') {
	- $console->writeOut(
	- "<bg:green> %s </bg> %s\n",
	- pht('BUILDS PASSED'),
	- pht('Harbormaster builds for the active diff completed successfully.'));
	- return;
	- }
	-
	- switch ($buildable['buildableStatus']) {
	- case 'building':
	- $message = pht(
	- 'Harbormaster is still building the active diff for this revision.');
	- $prompt = pht('Land revision anyway, despite ongoing build?');
	- break;
	- case 'failed':
	- $message = pht(
	- 'Harbormaster failed to build the active diff for this revision.');
	- $prompt = pht('Land revision anyway, despite build failures?');
	- break;
	- default:
	- // If we don't recognize the status, just bail.
	- return;
	- }
	-
	- $builds = $this->queryBuilds(
	- array(
	- 'buildablePHIDs' => array($buildable['phid']),
	- ));
	-
	- $console->writeOut($message."\n\n");
	-
	- $builds = msortv($builds, 'getStatusSortVector');
	- foreach ($builds as $build) {
	- $ansi_color = $build->getStatusANSIColor();
	- $status_name = $build->getStatusName();
	- $object_name = $build->getObjectName();
	- $build_name = $build->getName();
	-
	- echo tsprintf(
	- " <bg:".$ansi_color."> %s </bg> %s: %s\n",
	- $status_name,
	- $object_name,
	- $build_name);
	- }
	-
	- $console->writeOut(
	- "\n%s\n\n %s: __%s__",
	- pht('You can review build details here:'),
	- pht('Harbormaster URI'),
	- $buildable['uri']);
	-
	- if (!phutil_console_confirm($prompt)) {
	- throw new ArcanistUserAbortException();
	- }
	+ public function getLargeWorkingSetLimit() {
	+ return 50;
	}

	- private function checkForBuildablesWithPlanBehaviors($diff_phid) {
	- // TODO: These queries should page through all results instead of fetching
	- // only the first page, but we don't have good primitives to support that
	- // in "master" yet.
	-
	- $this->writeInfo(
	- pht('BUILDS'),
	- pht('Checking build status...'));
	-
	- $raw_buildables = $this->getConduit()->callMethodSynchronous(
	- 'harbormaster.buildable.search',
	- array(
	- 'constraints' => array(
	- 'objectPHIDs' => array(
	- $diff_phid,
	- ),
	- 'manual' => false,
	- ),
	- ));
	-
	- if (!$raw_buildables['data']) {
	- return;
	- }
	-
	- $buildables = $raw_buildables['data'];
	- $buildable_phids = ipull($buildables, 'phid');
	-
	- $raw_builds = $this->getConduit()->callMethodSynchronous(
	- 'harbormaster.build.search',
	- array(
	- 'constraints' => array(
	- 'buildables' => $buildable_phids,
	- ),
	- ));
	-
	- if (!$raw_builds['data']) {
	- return;
	- }
	-
	- $builds = array();
	- foreach ($raw_builds['data'] as $raw_build) {
	- $build_ref = ArcanistBuildRef::newFromConduit($raw_build);
	- $build_phid = $build_ref->getPHID();
	- $builds[$build_phid] = $build_ref;
	- }
	-
	- $plan_phids = mpull($builds, 'getBuildPlanPHID');
	- $plan_phids = array_values($plan_phids);
	-
	- $raw_plans = $this->getConduit()->callMethodSynchronous(
	- 'harbormaster.buildplan.search',
	- array(
	- 'constraints' => array(
	- 'phids' => $plan_phids,
	- ),
	- ));
	-
	- $plans = array();
	- foreach ($raw_plans['data'] as $raw_plan) {
	- $plan_ref = ArcanistBuildPlanRef::newFromConduit($raw_plan);
	- $plan_phid = $plan_ref->getPHID();
	- $plans[$plan_phid] = $plan_ref;
	- }
	-
	- $ongoing_builds = array();
	- $failed_builds = array();
	-
	- $builds = msortv($builds, 'getStatusSortVector');
	- foreach ($builds as $build_ref) {
	- $plan = idx($plans, $build_ref->getBuildPlanPHID());
	- if (!$plan) {
	- continue;
	- }
	-
	- $plan_behavior = $plan->getBehavior('arc-land', 'always');
	- $if_building = ($plan_behavior == 'building');
	- $if_complete = ($plan_behavior == 'complete');
	- $if_never = ($plan_behavior == 'never');
	-
	- // If the build plan "Never" warns when landing, skip it.
	- if ($if_never) {
	- continue;
	- }
	-
	- // If the build plan warns when landing "If Complete" but the build is
	- // not complete, skip it.
	- if ($if_complete && !$build_ref->isComplete()) {
	- continue;
	- }
	-
	- // If the build plan warns when landing "If Building" but the build is
	- // complete, skip it.
	- if ($if_building && $build_ref->isComplete()) {
	- continue;
	- }
	-
	- // Ignore passing builds.
	- if ($build_ref->isPassed()) {
	- continue;
	- }
	-
	- if (!$build_ref->isComplete()) {
	- $ongoing_builds[] = $build_ref;
	- } else {
	- $failed_builds[] = $build_ref;
	- }
	- }
	+ public function runWorkflow() {
	+ $working_copy = $this->getWorkingCopy();
	+ $repository_api = $working_copy->getRepositoryAPI();

	- if (!$ongoing_builds && !$failed_builds) {
	- return;
	- }
	-
	- if ($failed_builds) {
	- $this->writeWarn(
	- pht('BUILD FAILURES'),
	- pht(
	- 'Harbormaster failed to build the active diff for this revision:'));
	- $prompt = pht('Land revision anyway, despite build failures?');
	- } else if ($ongoing_builds) {
	- $this->writeWarn(
	- pht('ONGOING BUILDS'),
	+ $land_engine = $repository_api->getLandEngine();
	+ if (!$land_engine) {
	+ throw new PhutilArgumentUsageException(
	pht(
	- 'Harbormaster is still building the active diff for this revision:'));
	- $prompt = pht('Land revision anyway, despite ongoing build?');
	- }
	-
	- $show_builds = array_merge($failed_builds, $ongoing_builds);
	- echo "\n";
	- foreach ($show_builds as $build_ref) {
	- $ansi_color = $build_ref->getStatusANSIColor();
	- $status_name = $build_ref->getStatusName();
	- $object_name = $build_ref->getObjectName();
	- $build_name = $build_ref->getName();
	-
	- echo tsprintf(
	- " <bg:".$ansi_color."> %s </bg> %s: %s\n",
	- $status_name,
	- $object_name,
	- $build_name);
	- }
	-
	- echo tsprintf(
	- "\n%s\n\n",
	- pht('You can review build details here:'));
	-
	- foreach ($buildables as $buildable) {
	- $buildable_uri = id(new PhutilURI($this->getConduitURI()))
	- ->setPath(sprintf('/B%d', $buildable['id']));
	-
	- echo tsprintf(
	- " %s: __%s__\n",
	- pht('Buildable %d', $buildable['id']),
	- $buildable_uri);
	- }
	-
	- if (!phutil_console_confirm($prompt)) {
	- throw new ArcanistUserAbortException();
	- }
	- }
	-
	- public function buildEngineMessage(ArcanistLandEngine $engine) {
	- // TODO: This is oh-so-gross.
	- $this->findRevision();
	- $engine->setCommitMessageFile($this->messageFile);
	- }
	-
	- public function didCommitMerge() {
	- $this->dispatchEvent(
	- ArcanistEventType::TYPE_LAND_WILLPUSHREVISION,
	- array());
	- }
	-
	- public function didPush() {
	- $this->askForRepositoryUpdate();
	-
	- $mark_workflow = $this->buildChildWorkflow(
	- 'close-revision',
	- array(
	- '--finalize',
	- '--quiet',
	- $this->revision['id'],
	- ));
	- $mark_workflow->run();
	+ '"arc land" must be run in a Git or Mercurial working copy.'));
	+ }
	+
	+ $is_incremental = $this->getArgument('incremental');
	+ $source_refs = $this->getArgument('ref');
	+
	+ $onto_remote_arg = $this->getArgument('onto-remote');
	+ $onto_args = $this->getArgument('onto');
	+
	+ $into_remote = $this->getArgument('into-remote');
	+ $into_empty = $this->getArgument('into-empty');
	+ $into_local = $this->getArgument('into-local');
	+ $into = $this->getArgument('into');
	+
	+ $is_preview = $this->getArgument('preview');
	+ $should_hold = $this->getArgument('hold');
	+ $should_keep = $this->getArgument('keep-branches');
	+
	+ $revision = $this->getArgument('revision');
	+ $strategy = $this->getArgument('strategy');
	+
	+ $land_engine
	+ ->setViewer($this->getViewer())
	+ ->setWorkflow($this)
	+ ->setLogEngine($this->getLogEngine())
	+ ->setSourceRefs($source_refs)
	+ ->setShouldHold($should_hold)
	+ ->setShouldKeep($should_keep)
	+ ->setStrategyArgument($strategy)
	+ ->setShouldPreview($is_preview)
	+ ->setOntoRemoteArgument($onto_remote_arg)
	+ ->setOntoArguments($onto_args)
	+ ->setIntoRemoteArgument($into_remote)
	+ ->setIntoEmptyArgument($into_empty)
	+ ->setIntoLocalArgument($into_local)
	+ ->setIntoArgument($into)
	+ ->setIsIncremental($is_incremental)
	+ ->setRevisionSymbol($revision);
	+
	+ $land_engine->execute();
	}

	- private function queryBuilds(array $constraints) {
	- $conduit = $this->getConduit();
	-
	- // NOTE: This method only loads the 100 most recent builds. It's rare for
	- // a revision to have more builds than that and there's currently no paging
	- // wrapper for "*.search" Conduit API calls available in Arcanist.
	-
	- try {
	- $raw_result = $conduit->callMethodSynchronous(
	- 'harbormaster.build.search',
	- array(
	- 'constraints' => $constraints,
	- ));
	- } catch (Exception $ex) {
	- // If the server doesn't have "harbormaster.build.search" yet (Aug 2016),
	- // try the older "harbormaster.querybuilds" instead.
	- $raw_result = $conduit->callMethodSynchronous(
	- 'harbormaster.querybuilds',
	- $constraints);
	- }
	-
	- $refs = array();
	- foreach ($raw_result['data'] as $raw_data) {
	- $refs[] = ArcanistBuildRef::newFromConduit($raw_data);
	- }
	-
	- return $refs;
	- }
	-
	-
	}
	diff --git a/src/workflow/ArcanistWorkflow.php b/src/workflow/ArcanistWorkflow.php
	--- a/src/workflow/ArcanistWorkflow.php
	+++ b/src/workflow/ArcanistWorkflow.php
	@@ -244,7 +244,7 @@
	return $err;
	}

	- final protected function getLogEngine() {
	+ final public function getLogEngine() {
	return $this->getRuntime()->getLogEngine();
	}

	@@ -2357,6 +2357,15 @@
	$prompts = $this->newPrompts();
	assert_instances_of($prompts, 'ArcanistPrompt');

	+ $prompts[] = $this->newPrompt('arc.state.stash')
	+ ->setDescription(
	+ pht(
	+ 'Prompts the user to stash changes and continue when the '.
	+ 'working copy has untracked, uncommitted. or unstaged '.
	+ 'changes.'));
	+
	+ // TODO: Swap to ArrayCheck?
	+
	$map = array();
	foreach ($prompts as $prompt) {
	$key = $prompt->getKey();
	@@ -2380,7 +2389,7 @@
	return $this->promptMap;
	}

	- protected function getPrompt($key) {
	+ final public function getPrompt($key) {
	$map = $this->getPromptMap();

	$prompt = idx($map, $key);

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