diff --git a/src/repository/api/ArcanistMercurialAPI.php b/src/repository/api/ArcanistMercurialAPI.php
index d6d10a9e..7aaa04f7 100644
--- a/src/repository/api/ArcanistMercurialAPI.php
+++ b/src/repository/api/ArcanistMercurialAPI.php
@@ -1,1105 +1,1109 @@
 <?php
 
 /**
  * Interfaces with the Mercurial working copies.
  */
 final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
 
   private $branch;
   private $localCommitInfo;
   private $rawDiffCache = array();
 
   private $supportsRebase;
   private $supportsPhases;
 
   protected function buildLocalFuture(array $argv) {
     // Mercurial has a "defaults" feature which basically breaks automation by
     // allowing the user to add random flags to any command. This feature is
     // "deprecated" and "a bad idea" that you should "forget ... existed"
     // according to project lead Matt Mackall:
     //
     //  http://markmail.org/message/hl3d6eprubmkkqh5
     //
     // There is an HGPLAIN environmental variable which enables "plain mode"
     // and hopefully disables this stuff.
 
     if (phutil_is_windows()) {
       $argv[0] = 'set HGPLAIN=1 & hg '.$argv[0];
     } else {
       $argv[0] = 'HGPLAIN=1 hg '.$argv[0];
     }
 
     $future = newv('ExecFuture', $argv);
     $future->setCWD($this->getPath());
     return $future;
   }
 
   public function execPassthru($pattern /* , ... */) {
     $args = func_get_args();
     if (phutil_is_windows()) {
       $args[0] = 'hg '.$args[0];
     } else {
       $args[0] = 'HGPLAIN=1 hg '.$args[0];
     }
 
     return call_user_func_array('phutil_passthru', $args);
   }
 
   public function getSourceControlSystemName() {
     return 'hg';
   }
 
   public function getMetadataPath() {
     return $this->getPath('.hg');
   }
 
   public function getSourceControlBaseRevision() {
     return $this->getCanonicalRevisionName($this->getBaseCommit());
   }
 
   public function getCanonicalRevisionName($string) {
     $match = null;
     if ($this->isHgSubversionRepo() &&
         preg_match('/@([0-9]+)$/', $string, $match)) {
       $string = hgsprintf('svnrev(%s)', $match[1]);
     }
 
     list($stdout) = $this->execxLocal(
       'log -l 1 --template %s -r %s --',
       '{node}',
       $string);
     return $stdout;
   }
 
   public function getHashFromFromSVNRevisionNumber($revision_id) {
     $matches = array();
     $string = hgsprintf('svnrev(%s)', $revision_id);
     list($stdout) = $this->execxLocal(
       'log -l 1 --template %s -r %s --',
       '{node}',
        $string);
     if (!$stdout) {
       throw new ArcanistUsageException(
         pht('Cannot find the HG equivalent of %s given.', $revision_id));
     }
     return $stdout;
   }
 
 
   public function getSVNRevisionNumberFromHash($hash) {
     $matches = array();
     list($stdout) = $this->execxLocal(
       'log -r %s --template {svnrev}', $hash);
     if (!$stdout) {
       throw new ArcanistUsageException(
         pht('Cannot find the SVN equivalent of %s given.', $hash));
     }
     return $stdout;
   }
 
   public function getSourceControlPath() {
     return '/';
   }
 
   public function getBranchName() {
     if (!$this->branch) {
       list($stdout) = $this->execxLocal('branch');
       $this->branch = trim($stdout);
     }
     return $this->branch;
   }
 
   protected function didReloadCommitRange() {
     $this->localCommitInfo = null;
   }
 
   protected function buildBaseCommit($symbolic_commit) {
     if ($symbolic_commit !== null) {
       try {
         $commit = $this->getCanonicalRevisionName(
           hgsprintf('ancestor(%s,.)', $symbolic_commit));
       } catch (Exception $ex) {
         // Try it as a revset instead of a commit id
         try {
           $commit = $this->getCanonicalRevisionName(
             hgsprintf('ancestor(%R,.)', $symbolic_commit));
         } catch (Exception $ex) {
           throw new ArcanistUsageException(
             pht(
               "Commit '%s' is not a valid Mercurial commit identifier.",
               $symbolic_commit));
         }
       }
 
       $this->setBaseCommitExplanation(
         pht(
           'it is the greatest common ancestor of the working directory '.
           'and the commit you specified explicitly.'));
       return $commit;
     }
 
     if ($this->getBaseCommitArgumentRules() ||
         $this->getConfigurationManager()->getConfigFromAnySource('base')) {
       $base = $this->resolveBaseCommit();
       if (!$base) {
         throw new ArcanistUsageException(
           pht(
             "None of the rules in your 'base' configuration matched a valid ".
             "commit. Adjust rules or specify which commit you want to use ".
             "explicitly."));
       }
       return $base;
     }
 
     // Mercurial 2.1 and up have phases which indicate if something is
     // published or not. To find which revs are outgoing, it's much
     // faster to check the phase instead of actually checking the server.
     if ($this->supportsPhases()) {
       list($err, $stdout) = $this->execManualLocal(
         'log --branch %s -r %s --style default',
         $this->getBranchName(),
         'draft()');
     } else {
       list($err, $stdout) = $this->execManualLocal(
         'outgoing --branch %s --style default',
         $this->getBranchName());
     }
 
     if (!$err) {
       $logs = ArcanistMercurialParser::parseMercurialLog($stdout);
     } else {
       // Mercurial (in some versions?) raises an error when there's nothing
       // outgoing.
       $logs = array();
     }
 
     if (!$logs) {
       $this->setBaseCommitExplanation(
         pht(
           'you have no outgoing commits, so arc assumes you intend to submit '.
           'uncommitted changes in the working copy.'));
       return $this->getWorkingCopyRevision();
     }
 
     $outgoing_revs = ipull($logs, 'rev');
 
     // This is essentially an implementation of a theoretical `hg merge-base`
     // command.
     $against = $this->getWorkingCopyRevision();
     while (true) {
       // NOTE: The "^" and "~" syntaxes were only added in hg 1.9, which is
       // new as of July 2011, so do this in a compatible way. Also, "hg log"
       // and "hg outgoing" don't necessarily show parents (even if given an
       // explicit template consisting of just the parents token) so we need
       // to separately execute "hg parents".
 
       list($stdout) = $this->execxLocal(
         'parents --style default --rev %s',
         $against);
       $parents_logs = ArcanistMercurialParser::parseMercurialLog($stdout);
 
       list($p1, $p2) = array_merge($parents_logs, array(null, null));
 
       if ($p1 && !in_array($p1['rev'], $outgoing_revs)) {
         $against = $p1['rev'];
         break;
       } else if ($p2 && !in_array($p2['rev'], $outgoing_revs)) {
         $against = $p2['rev'];
         break;
       } else if ($p1) {
         $against = $p1['rev'];
       } else {
         // This is the case where you have a new repository and the entire
         // thing is outgoing; Mercurial literally accepts "--rev null" as
         // meaning "diff against the empty state".
         $against = 'null';
         break;
       }
     }
 
     if ($against == 'null') {
       $this->setBaseCommitExplanation(
         pht('this is a new repository (all changes are outgoing).'));
     } else {
       $this->setBaseCommitExplanation(
         pht(
           'it is the first commit reachable from the working copy state '.
           'which is not outgoing.'));
     }
 
     return $against;
   }
 
   public function getLocalCommitInformation() {
     if ($this->localCommitInfo === null) {
       $base_commit = $this->getBaseCommit();
       list($info) = $this->execxLocal(
         'log --template %s --rev %s --branch %s --',
         "{node}\1{rev}\1{author}\1".
           "{date|rfc822date}\1{branch}\1{tag}\1{parents}\1{desc}\2",
         hgsprintf('(%s::. - %s)', $base_commit, $base_commit),
         $this->getBranchName());
       $logs = array_filter(explode("\2", $info));
 
       $last_node = null;
 
       $futures = array();
 
       $commits = array();
       foreach ($logs as $log) {
         list($node, $rev, $full_author, $date, $branch, $tag,
           $parents, $desc) = explode("\1", $log, 9);
 
         list($author, $author_email) = $this->parseFullAuthor($full_author);
 
         // NOTE: If a commit has only one parent, {parents} returns empty.
         // If it has two parents, {parents} returns revs and short hashes, not
         // full hashes. Try to avoid making calls to "hg parents" because it's
         // relatively expensive.
         $commit_parents = null;
         if (!$parents) {
           if ($last_node) {
             $commit_parents = array($last_node);
           }
         }
 
         if (!$commit_parents) {
           // We didn't get a cheap hit on previous commit, so do the full-cost
           // "hg parents" call. We can run these in parallel, at least.
           $futures[$node] = $this->execFutureLocal(
             'parents --template %s --rev %s',
             '{node}\n',
             $node);
         }
 
         $commits[$node] = array(
           'author'  => $author,
           'time'    => strtotime($date),
           'branch'  => $branch,
           'tag'     => $tag,
           'commit'  => $node,
           'rev'     => $node, // TODO: Remove eventually.
           'local'   => $rev,
           'parents' => $commit_parents,
           'summary' => head(explode("\n", $desc)),
           'message' => $desc,
           'authorEmail' => $author_email,
         );
 
         $last_node = $node;
       }
 
       $futures = id(new FutureIterator($futures))
         ->limit(4);
       foreach ($futures as $node => $future) {
         list($parents) = $future->resolvex();
         $parents = array_filter(explode("\n", $parents));
         $commits[$node]['parents'] = $parents;
       }
 
       // Put commits in newest-first order, to be consistent with Git and the
       // expected order of "hg log" and "git log" under normal circumstances.
       // The order of ancestors() is oldest-first.
       $commits = array_reverse($commits);
 
       $this->localCommitInfo = $commits;
     }
 
     return $this->localCommitInfo;
   }
 
   public function getAllFiles() {
     // TODO: Handle paths with newlines.
     $future = $this->buildLocalFuture(array('manifest'));
     return new LinesOfALargeExecFuture($future);
   }
 
   public function getChangedFiles($since_commit) {
     list($stdout) = $this->execxLocal(
       'status --rev %s',
       $since_commit);
     return ArcanistMercurialParser::parseMercurialStatus($stdout);
   }
 
   public function getBlame($path) {
     list($stdout) = $this->execxLocal(
       'annotate -u -v -c --rev %s -- %s',
       $this->getBaseCommit(),
       $path);
 
     $lines = phutil_split_lines($stdout, $retain_line_endings = true);
 
     $blame = array();
     foreach ($lines as $line) {
       if (!strlen($line)) {
         continue;
       }
 
       $matches = null;
       $ok = preg_match('/^\s*([^:]+?) ([a-f0-9]{12}):/', $line, $matches);
 
       if (!$ok) {
         throw new Exception(
           pht(
             'Unable to parse Mercurial blame line: %s',
             $line));
       }
 
       $revision = $matches[2];
       $author = trim($matches[1]);
       $blame[] = array($author, $revision);
     }
 
     return $blame;
   }
 
   protected function buildUncommittedStatus() {
     list($stdout) = $this->execxLocal('status');
 
     $results = new PhutilArrayWithDefaultValue();
 
     $working_status = ArcanistMercurialParser::parseMercurialStatus($stdout);
     foreach ($working_status as $path => $mask) {
       if (!($mask & parent::FLAG_UNTRACKED)) {
         // Mark tracked files as uncommitted.
         $mask |= self::FLAG_UNCOMMITTED;
       }
 
       $results[$path] |= $mask;
     }
 
     return $results->toArray();
   }
 
   protected function buildCommitRangeStatus() {
     list($stdout) = $this->execxLocal(
       'status --rev %s --rev tip',
       $this->getBaseCommit());
 
     $results = new PhutilArrayWithDefaultValue();
 
     $working_status = ArcanistMercurialParser::parseMercurialStatus($stdout);
     foreach ($working_status as $path => $mask) {
       $results[$path] |= $mask;
     }
 
     return $results->toArray();
   }
 
   protected function didReloadWorkingCopy() {
     // Diffs are against ".", so we need to drop the cache if we change the
     // working copy.
     $this->rawDiffCache = array();
     $this->branch = null;
   }
 
   private function getDiffOptions() {
     $options = array(
       '--git',
       '-U'.$this->getDiffLinesOfContext(),
     );
     return implode(' ', $options);
   }
 
   public function getRawDiffText($path) {
     $options = $this->getDiffOptions();
 
     $range = $this->getBaseCommit();
 
     $raw_diff_cache_key = $options.' '.$range.' '.$path;
     if (idx($this->rawDiffCache, $raw_diff_cache_key)) {
       return idx($this->rawDiffCache, $raw_diff_cache_key);
     }
 
     list($stdout) = $this->execxLocal(
       'diff %C --rev %s -- %s',
       $options,
       $range,
       $path);
 
     $this->rawDiffCache[$raw_diff_cache_key] = $stdout;
 
     return $stdout;
   }
 
   public function getFullMercurialDiff() {
     return $this->getRawDiffText('');
   }
 
   public function getOriginalFileData($path) {
     return $this->getFileDataAtRevision($path, $this->getBaseCommit());
   }
 
   public function getCurrentFileData($path) {
     return $this->getFileDataAtRevision(
       $path,
       $this->getWorkingCopyRevision());
   }
 
   public function getBulkOriginalFileData($paths) {
     return $this->getBulkFileDataAtRevision($paths, $this->getBaseCommit());
   }
 
   public function getBulkCurrentFileData($paths) {
     return $this->getBulkFileDataAtRevision(
       $paths,
       $this->getWorkingCopyRevision());
   }
 
   private function getBulkFileDataAtRevision($paths, $revision) {
     // Calling 'hg cat' on each file individually is slow (1 second per file
     // on a large repo) because mercurial has to decompress and parse the
     // entire manifest every time. Do it in one large batch instead.
 
     // hg cat will write the file data to files in a temp directory
     $tmpdir = Filesystem::createTemporaryDirectory();
 
     // Mercurial doesn't create the directories for us :(
     foreach ($paths as $path) {
       $tmppath = $tmpdir.'/'.$path;
       Filesystem::createDirectory(dirname($tmppath), 0755, true);
     }
 
+    // NOTE: The "%s%%p" construction passes a literal "%p" to Mercurial,
+    // which is a formatting directive for a repo-relative filepath. The
+    // particulars of the construction avoid Windows escaping issues. See
+    // PHI904.
+
     list($err, $stdout) = $this->execManualLocal(
-      'cat --rev %s --output %s -- %C',
+      'cat --rev %s --output %s%%p -- %Ls',
       $revision,
-      // %p is the formatter for the repo-relative filepath
-      $tmpdir.'/%p',
-      implode(' ', $paths));
+      $tmpdir.DIRECTORY_SEPARATOR,
+      $paths);
 
     $filedata = array();
     foreach ($paths as $path) {
       $tmppath = $tmpdir.'/'.$path;
       if (Filesystem::pathExists($tmppath)) {
         $filedata[$path] = Filesystem::readFile($tmppath);
       }
     }
 
     Filesystem::remove($tmpdir);
 
     return $filedata;
   }
 
   private function getFileDataAtRevision($path, $revision) {
     list($err, $stdout) = $this->execManualLocal(
       'cat --rev %s -- %s',
       $revision,
       $path);
     if ($err) {
       // Assume this is "no file at revision", i.e. a deleted or added file.
       return null;
     } else {
       return $stdout;
     }
   }
 
   public function getWorkingCopyRevision() {
     return '.';
   }
 
   public function isHistoryDefaultImmutable() {
     return true;
   }
 
   public function supportsAmend() {
     list($err, $stdout) = $this->execManualLocal('help commit');
     if ($err) {
       return false;
     } else {
       return (strpos($stdout, 'amend') !== false);
     }
   }
 
   public function supportsRebase() {
     if ($this->supportsRebase === null) {
       list($err) = $this->execManualLocal('help rebase');
       $this->supportsRebase = $err === 0;
     }
 
     return $this->supportsRebase;
   }
 
   public function supportsPhases() {
     if ($this->supportsPhases === null) {
       list($err) = $this->execManualLocal('help phase');
       $this->supportsPhases = $err === 0;
     }
 
     return $this->supportsPhases;
   }
 
   public function supportsCommitRanges() {
     return true;
   }
 
   public function supportsLocalCommits() {
     return true;
   }
 
   public function getAllBranches() {
     list($branch_info) = $this->execxLocal('bookmarks');
     if (trim($branch_info) == 'no bookmarks set') {
       return array();
     }
 
     $matches = null;
     preg_match_all(
       '/^\s*(\*?)\s*(.+)\s(\S+)$/m',
       $branch_info,
       $matches,
       PREG_SET_ORDER);
 
     $return = array();
     foreach ($matches as $match) {
       list(, $current, $name) = $match;
       $return[] = array(
         'current' => (bool)$current,
         'name'    => rtrim($name),
       );
     }
     return $return;
   }
 
   public function hasLocalCommit($commit) {
     try {
       $this->getCanonicalRevisionName($commit);
       return true;
     } catch (Exception $ex) {
       return false;
     }
   }
 
   public function getCommitMessage($commit) {
     list($message) = $this->execxLocal(
       'log --template={desc} --rev %s',
       $commit);
     return $message;
   }
 
   public function getAllLocalChanges() {
     $diff = $this->getFullMercurialDiff();
     if (!strlen(trim($diff))) {
       return array();
     }
     $parser = new ArcanistDiffParser();
     return $parser->parseDiff($diff);
   }
 
   public function supportsLocalBranchMerge() {
     return true;
   }
 
   public function performLocalBranchMerge($branch, $message) {
     if ($branch) {
       $err = phutil_passthru(
         '(cd %s && HGPLAIN=1 hg merge --rev %s && hg commit -m %s)',
         $this->getPath(),
         $branch,
         $message);
     } else {
       $err = phutil_passthru(
         '(cd %s && HGPLAIN=1 hg merge && hg commit -m %s)',
         $this->getPath(),
         $message);
     }
 
     if ($err) {
       throw new ArcanistUsageException(pht('Merge failed!'));
     }
   }
 
   public function getFinalizedRevisionMessage() {
     return pht(
       "You may now push this commit upstream, as appropriate (e.g. with ".
       "'%s' or by printing and faxing it).",
       'hg push');
   }
 
   public function getCommitMessageLog() {
     $base_commit = $this->getBaseCommit();
     list($stdout) = $this->execxLocal(
       'log --template %s --rev %s --branch %s --',
       "{node}\1{desc}\2",
       hgsprintf('(%s::. - %s)', $base_commit, $base_commit),
       $this->getBranchName());
 
     $map = array();
 
     $logs = explode("\2", trim($stdout));
     foreach (array_filter($logs) as $log) {
       list($node, $desc) = explode("\1", $log);
       $map[$node] = $desc;
     }
 
     return array_reverse($map);
   }
 
   public function loadWorkingCopyDifferentialRevisions(
     ConduitClient $conduit,
     array $query) {
 
     $messages = $this->getCommitMessageLog();
     $parser = new ArcanistDiffParser();
 
     // First, try to find revisions by explicit revision IDs in commit messages.
     $reason_map = array();
     $revision_ids = array();
     foreach ($messages as $node_id => $message) {
       $object = ArcanistDifferentialCommitMessage::newFromRawCorpus($message);
 
       if ($object->getRevisionID()) {
         $revision_ids[] = $object->getRevisionID();
         $reason_map[$object->getRevisionID()] = $node_id;
       }
     }
 
     if ($revision_ids) {
       $results = $conduit->callMethodSynchronous(
         'differential.query',
         $query + array(
           'ids' => $revision_ids,
         ));
 
       foreach ($results as $key => $result) {
         $hash = substr($reason_map[$result['id']], 0, 16);
         $results[$key]['why'] =
           pht(
             "Commit message for '%s' has explicit 'Differential Revision'.",
             $hash);
       }
 
       return $results;
     }
 
     // Try to find revisions by hash.
     $hashes = array();
     foreach ($this->getLocalCommitInformation() as $commit) {
       $hashes[] = array('hgcm', $commit['commit']);
     }
 
     if ($hashes) {
 
       // NOTE: In the case of "arc diff . --uncommitted" in a Mercurial working
       // copy with dirty changes, there may be no local commits.
 
       $results = $conduit->callMethodSynchronous(
         'differential.query',
         $query + array(
           'commitHashes' => $hashes,
         ));
 
       foreach ($results as $key => $hash) {
         $results[$key]['why'] = pht(
           'A mercurial commit hash in the commit range is already attached '.
           'to the Differential revision.');
       }
 
       return $results;
     }
 
     return array();
   }
 
   public function updateWorkingCopy() {
     $this->execxLocal('up');
     $this->reloadWorkingCopy();
   }
 
   private function getMercurialConfig($key, $default = null) {
     list($stdout) = $this->execxLocal('showconfig %s', $key);
     if ($stdout == '') {
       return $default;
     }
     return rtrim($stdout);
   }
 
   public function getAuthor() {
     $full_author = $this->getMercurialConfig('ui.username');
     list($author, $author_email) = $this->parseFullAuthor($full_author);
     return $author;
   }
 
   /**
    * Parse the Mercurial author field.
    *
    * Not everyone enters their email address as a part of the username
    * field. Try to make it work when it's obvious.
    *
    * @param string $full_author
    * @return array
    */
   protected function parseFullAuthor($full_author) {
     if (strpos($full_author, '@') === false) {
       $author = $full_author;
       $author_email = null;
     } else {
       $email = new PhutilEmailAddress($full_author);
       $author = $email->getDisplayName();
       $author_email = $email->getAddress();
     }
 
     return array($author, $author_email);
   }
 
   public function addToCommit(array $paths) {
     $this->execxLocal(
       'addremove -- %Ls',
       $paths);
     $this->reloadWorkingCopy();
   }
 
   public function doCommit($message) {
     $tmp_file = new TempFile();
     Filesystem::writeFile($tmp_file, $message);
     $this->execxLocal('commit -l %s', $tmp_file);
     $this->reloadWorkingCopy();
   }
 
   public function amendCommit($message = null) {
     if ($message === null) {
       $message = $this->getCommitMessage('.');
     }
 
     $tmp_file = new TempFile();
     Filesystem::writeFile($tmp_file, $message);
 
     try {
       $this->execxLocal(
         'commit --amend -l %s',
         $tmp_file);
     } catch (CommandException $ex) {
       if (preg_match('/nothing changed/', $ex->getStdout())) {
         // NOTE: Mercurial considers it an error to make a no-op amend. Although
         // we generally defer to the underlying VCS to dictate behavior, this
         // one seems a little goofy, and we use amend as part of various
         // workflows under the assumption that no-op amends are fine. If this
         // amend failed because it's a no-op, just continue.
       } else {
         throw $ex;
       }
     }
 
     $this->reloadWorkingCopy();
   }
 
   public function getCommitSummary($commit) {
     if ($commit == 'null') {
       return pht('(The Empty Void)');
     }
 
     list($summary) = $this->execxLocal(
       'log --template {desc} --limit 1 --rev %s',
       $commit);
 
     $summary = head(explode("\n", $summary));
 
     return trim($summary);
   }
 
   public function backoutCommit($commit_hash) {
     $this->execxLocal('backout -r %s', $commit_hash);
     $this->reloadWorkingCopy();
     if (!$this->getUncommittedStatus()) {
       throw new ArcanistUsageException(
         pht('%s has already been reverted.', $commit_hash));
     }
   }
 
   public function getBackoutMessage($commit_hash) {
     return pht('Backed out changeset %s,', $commit_hash);
   }
 
   public function resolveBaseCommitRule($rule, $source) {
     list($type, $name) = explode(':', $rule, 2);
 
     // NOTE: This function MUST return node hashes or symbolic commits (like
     // branch names or the word "tip"), not revsets. This includes ".^" and
     // similar, which a revset, not a symbolic commit identifier. If you return
     // a revset it will be escaped later and looked up literally.
 
     switch ($type) {
       case 'hg':
         $matches = null;
         if (preg_match('/^gca\((.+)\)$/', $name, $matches)) {
           list($err, $merge_base) = $this->execManualLocal(
             'log --template={node} --rev %s',
             sprintf('ancestor(., %s)', $matches[1]));
           if (!$err) {
             $this->setBaseCommitExplanation(
               pht(
                 "it is the greatest common ancestor of '%s' and %s, as ".
                 "specified by '%s' in your %s 'base' configuration.",
                 $matches[1],
                 '.',
                 $rule,
                 $source));
             return trim($merge_base);
           }
         } else {
           list($err, $commit) = $this->execManualLocal(
             'log --template {node} --rev %s',
             hgsprintf('%s', $name));
 
           if ($err) {
             list($err, $commit) = $this->execManualLocal(
               'log --template {node} --rev %s',
               $name);
           }
           if (!$err) {
             $this->setBaseCommitExplanation(
               pht(
                 "it is specified by '%s' in your %s 'base' configuration.",
                 $rule,
                 $source));
             return trim($commit);
           }
         }
         break;
       case 'arc':
         switch ($name) {
           case 'empty':
             $this->setBaseCommitExplanation(
               pht(
                 "you specified '%s' in your %s 'base' configuration.",
                 $rule,
                 $source));
             return 'null';
           case 'outgoing':
             list($err, $outgoing_base) = $this->execManualLocal(
               'log --template={node} --rev %s',
               'limit(reverse(ancestors(.) - outgoing()), 1)');
             if (!$err) {
               $this->setBaseCommitExplanation(
                 pht(
                   "it is the first ancestor of the working copy that is not ".
                   "outgoing, and it matched the rule %s in your %s ".
                   "'base' configuration.",
                   $rule,
                   $source));
               return trim($outgoing_base);
             }
           case 'amended':
             $text = $this->getCommitMessage('.');
             $message = ArcanistDifferentialCommitMessage::newFromRawCorpus(
               $text);
             if ($message->getRevisionID()) {
               $this->setBaseCommitExplanation(
                 pht(
                   "'%s' has been amended with 'Differential Revision:', ".
                   "as specified by '%s' in your %s 'base' configuration.",
                   '.'.
                   $rule,
                   $source));
               // NOTE: This should be safe because Mercurial doesn't support
               // amend until 2.2.
               return $this->getCanonicalRevisionName('.^');
             }
             break;
           case 'bookmark':
             $revset =
               'limit('.
               '  sort('.
               '    (ancestors(.) and bookmark() - .) or'.
               '    (ancestors(.) - outgoing()), '.
               '  -rev),'.
               '1)';
             list($err, $bookmark_base) = $this->execManualLocal(
               'log --template={node} --rev %s',
               $revset);
             if (!$err) {
               $this->setBaseCommitExplanation(
                 pht(
                   "it is the first ancestor of %s that either has a bookmark, ".
                   "or is already in the remote and it matched the rule %s in ".
                   "your %s 'base' configuration",
                   '.',
                   $rule,
                   $source));
               return trim($bookmark_base);
             }
             break;
           case 'this':
             $this->setBaseCommitExplanation(
               pht(
                 "you specified '%s' in your %s 'base' configuration.",
                 $rule,
                 $source));
             return $this->getCanonicalRevisionName('.^');
           default:
             if (preg_match('/^nodiff\((.+)\)$/', $name, $matches)) {
               list($results) = $this->execxLocal(
                 'log --template %s --rev %s',
                 "{node}\1{desc}\2",
                 sprintf('ancestor(.,%s)::.^', $matches[1]));
               $results = array_reverse(explode("\2", trim($results)));
 
               foreach ($results as $result) {
                 if (empty($result)) {
                   continue;
                 }
 
                 list($node, $desc) = explode("\1", $result, 2);
 
                 $message = ArcanistDifferentialCommitMessage::newFromRawCorpus(
                   $desc);
                 if ($message->getRevisionID()) {
                   $this->setBaseCommitExplanation(
                     pht(
                       "it is the first ancestor of %s that has a diff and is ".
                       "the gca or a descendant of the gca with '%s', ".
                       "specified by '%s' in your %s 'base' configuration.",
                       '.',
                       $matches[1],
                       $rule,
                       $source));
                   return $node;
                 }
               }
             }
             break;
           }
         break;
       default:
         return null;
     }
 
     return null;
 
   }
 
   public function isHgSubversionRepo() {
     return file_exists($this->getPath('.hg/svn/rev_map'));
   }
 
   public function getSubversionInfo() {
     $info = array();
     $base_path = null;
     $revision = null;
     list($err, $raw_info) = $this->execManualLocal('svn info');
     if (!$err) {
       foreach (explode("\n", trim($raw_info)) as $line) {
         list($key, $value) = explode(': ', $line, 2);
         switch ($key) {
           case 'URL':
             $info['base_path'] = $value;
             $base_path = $value;
             break;
           case 'Repository UUID':
             $info['uuid'] = $value;
             break;
           case 'Revision':
             $revision = $value;
             break;
           default:
             break;
         }
       }
       if ($base_path && $revision) {
         $info['base_revision'] = $base_path.'@'.$revision;
       }
     }
     return $info;
   }
 
   public function getActiveBookmark() {
     $bookmarks = $this->getBookmarks();
     foreach ($bookmarks as $bookmark) {
       if ($bookmark['is_active']) {
         return $bookmark['name'];
       }
     }
 
     return null;
   }
 
   public function isBookmark($name) {
     $bookmarks = $this->getBookmarks();
     foreach ($bookmarks as $bookmark) {
       if ($bookmark['name'] === $name) {
         return true;
       }
     }
 
     return false;
   }
 
   public function isBranch($name) {
     $branches = $this->getBranches();
     foreach ($branches as $branch) {
       if ($branch['name'] === $name) {
         return true;
       }
     }
 
     return false;
   }
 
   public function getBranches() {
     list($stdout) = $this->execxLocal('--debug branches');
     $lines = ArcanistMercurialParser::parseMercurialBranches($stdout);
 
     $branches = array();
     foreach ($lines as $name => $spec) {
       $branches[] = array(
         'name' => $name,
         'revision' => $spec['rev'],
       );
     }
 
     return $branches;
   }
 
   public function getBookmarks() {
     $bookmarks = array();
 
     list($raw_output) = $this->execxLocal('bookmarks');
     $raw_output = trim($raw_output);
     if ($raw_output !== 'no bookmarks set') {
       foreach (explode("\n", $raw_output) as $line) {
         // example line:  * mybook               2:6b274d49be97
         list($name, $revision) = $this->splitBranchOrBookmarkLine($line);
 
         $is_active = false;
         if ('*' === $name[0]) {
           $is_active = true;
           $name = substr($name, 2);
         }
 
         $bookmarks[] = array(
           'is_active' => $is_active,
           'name' => $name,
           'revision' => $revision,
         );
       }
     }
 
     return $bookmarks;
   }
 
   private function splitBranchOrBookmarkLine($line) {
     // branches and bookmarks are printed in the format:
     // default                 0:a5ead76cdf85 (inactive)
     // * mybook               2:6b274d49be97
     // this code divides the name half from the revision half
     // it does not parse the * and (inactive) bits
     $colon_index = strrpos($line, ':');
     $before_colon = substr($line, 0, $colon_index);
     $start_rev_index = strrpos($before_colon, ' ');
     $name = substr($line, 0, $start_rev_index);
     $rev = substr($line, $start_rev_index);
 
     return array(trim($name), trim($rev));
   }
 
   public function getRemoteURI() {
     list($stdout) = $this->execxLocal('paths default');
 
     $stdout = trim($stdout);
     if (strlen($stdout)) {
       return $stdout;
     }
 
     return null;
   }
 
 }