diff --git a/src/applications/diffusion/controller/DiffusionBrowseController.php b/src/applications/diffusion/controller/DiffusionBrowseController.php
index 153906b25c..d762c60c55 100644
--- a/src/applications/diffusion/controller/DiffusionBrowseController.php
+++ b/src/applications/diffusion/controller/DiffusionBrowseController.php
@@ -1,1939 +1,1955 @@
 <?php
 
 final class DiffusionBrowseController extends DiffusionController {
 
   private $lintCommit;
   private $lintMessages;
   private $coverage;
 
   public function shouldAllowPublic() {
     return true;
   }
 
   public function handleRequest(AphrontRequest $request) {
     $response = $this->loadDiffusionContext();
     if ($response) {
       return $response;
     }
 
     $drequest = $this->getDiffusionRequest();
 
     // Figure out if we're browsing a directory, a file, or a search result
     // list.
 
     $grep = $request->getStr('grep');
     $find = $request->getStr('find');
     if (strlen($grep) || strlen($find)) {
       return $this->browseSearch();
     }
 
     $pager = id(new PHUIPagerView())
       ->readFromRequest($request);
 
     $results = DiffusionBrowseResultSet::newFromConduit(
       $this->callConduitWithDiffusionRequest(
         'diffusion.browsequery',
         array(
           'path' => $drequest->getPath(),
           'commit' => $drequest->getStableCommit(),
           'offset' => $pager->getOffset(),
           'limit' => $pager->getPageSize() + 1,
         )));
 
     $reason = $results->getReasonForEmptyResultSet();
     $is_file = ($reason == DiffusionBrowseResultSet::REASON_IS_FILE);
 
     if ($is_file) {
       return $this->browseFile($results);
     } else {
       $paths = $results->getPaths();
       $paths = $pager->sliceResults($paths);
       $results->setPaths($paths);
 
       return $this->browseDirectory($results, $pager);
     }
   }
 
   private function browseSearch() {
 
     $drequest = $this->getDiffusionRequest();
     $header = $this->buildHeaderView($drequest);
 
     $search_form = $this->renderSearchForm();
     $search_results = $this->renderSearchResults();
 
     $search_form = id(new PHUIObjectBoxView())
       ->setHeaderText(pht('Search'))
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->appendChild($search_form);
 
     $crumbs = $this->buildCrumbs(
       array(
         'branch' => true,
         'path'   => true,
         'view'   => 'browse',
       ));
     $crumbs->setBorder(true);
 
     $view = id(new PHUITwoColumnView())
       ->setHeader($header)
       ->setFooter(array(
           $search_form,
           $search_results,
         ));
 
     return $this->newPage()
       ->setTitle(
         array(
           nonempty(basename($drequest->getPath()), '/'),
           $drequest->getRepository()->getDisplayName(),
         ))
       ->setCrumbs($crumbs)
       ->appendChild($view);
   }
 
   private function browseFile() {
     $viewer = $this->getViewer();
     $request = $this->getRequest();
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     $before = $request->getStr('before');
     if ($before) {
       return $this->buildBeforeResponse($before);
     }
 
     $path = $drequest->getPath();
 
     $blame_key = PhabricatorDiffusionBlameSetting::SETTINGKEY;
 
     $show_blame = $request->getBool(
       'blame',
       $viewer->getUserSetting($blame_key));
 
     $view = $request->getStr('view');
     if ($request->isFormPost() && $view != 'raw' && $viewer->isLoggedIn()) {
       $preferences = PhabricatorUserPreferences::loadUserPreferences($viewer);
 
       $editor = id(new PhabricatorUserPreferencesEditor())
         ->setActor($viewer)
         ->setContentSourceFromRequest($request)
         ->setContinueOnNoEffect(true)
         ->setContinueOnMissingFields(true);
 
       $xactions = array();
       $xactions[] = $preferences->newTransaction($blame_key, $show_blame);
       $editor->applyTransactions($preferences, $xactions);
 
       $uri = $request->getRequestURI()
         ->alter('blame', null);
 
       return id(new AphrontRedirectResponse())->setURI($uri);
     }
 
     // We need the blame information if blame is on and this is an Ajax request.
     // If blame is on and this is a colorized request, we don't show blame at
     // first (we ajax it in afterward) so we don't need to query for it.
     $needs_blame = ($show_blame && $request->isAjax());
 
     $params = array(
       'commit' => $drequest->getCommit(),
       'path' => $drequest->getPath(),
     );
 
     $byte_limit = null;
     if ($view !== 'raw') {
       $byte_limit = PhabricatorFileStorageEngine::getChunkThreshold();
       $time_limit = 10;
 
       $params += array(
         'timeout' => $time_limit,
         'byteLimit' => $byte_limit,
       );
     }
 
     $response = $this->callConduitWithDiffusionRequest(
       'diffusion.filecontentquery',
       $params);
 
     $hit_byte_limit = $response['tooHuge'];
     $hit_time_limit = $response['tooSlow'];
 
     $file_phid = $response['filePHID'];
     if ($hit_byte_limit) {
       $corpus = $this->buildErrorCorpus(
         pht(
           'This file is larger than %s byte(s), and too large to display '.
           'in the web UI.',
           phutil_format_bytes($byte_limit)));
     } else if ($hit_time_limit) {
       $corpus = $this->buildErrorCorpus(
         pht(
           'This file took too long to load from the repository (more than '.
           '%s second(s)).',
           new PhutilNumber($time_limit)));
     } else {
       $file = id(new PhabricatorFileQuery())
         ->setViewer($viewer)
         ->withPHIDs(array($file_phid))
         ->executeOne();
       if (!$file) {
         throw new Exception(pht('Failed to load content file!'));
       }
 
       if ($view === 'raw') {
         return $file->getRedirectResponse();
       }
 
       $data = $file->loadFileData();
 
       $lfs_ref = $this->getGitLFSRef($repository, $data);
       if ($lfs_ref) {
         if ($view == 'git-lfs') {
           $file = $this->loadGitLFSFile($lfs_ref);
 
           // Rename the file locally so we generate a better vanity URI for
           // it. In storage, it just has a name like "lfs-13f9a94c0923...",
           // since we don't get any hints about possible human-readable names
           // at upload time.
           $basename = basename($drequest->getPath());
           $file->makeEphemeral();
           $file->setName($basename);
 
           return $file->getRedirectResponse();
         } else {
           $corpus = $this->buildGitLFSCorpus($lfs_ref);
         }
       } else if (ArcanistDiffUtils::isHeuristicBinaryFile($data)) {
         $file_uri = $file->getBestURI();
 
         if ($file->isViewableImage()) {
           $corpus = $this->buildImageCorpus($file_uri);
         } else {
           $corpus = $this->buildBinaryCorpus($file_uri, $data);
         }
       } else {
         $this->loadLintMessages();
         $this->coverage = $drequest->loadCoverage();
 
         // Build the content of the file.
         $corpus = $this->buildCorpus(
           $show_blame,
           $data,
           $needs_blame,
           $drequest,
           $path,
           $data);
       }
     }
 
     if ($request->isAjax()) {
       return id(new AphrontAjaxResponse())->setContent($corpus);
     }
 
     require_celerity_resource('diffusion-source-css');
 
     // Render the page.
     $view = $this->buildCurtain($drequest);
     $curtain = $this->enrichCurtain(
       $view,
       $drequest,
       $show_blame);
 
     $properties = $this->buildPropertyView($drequest);
     $header = $this->buildHeaderView($drequest);
     $header->setHeaderIcon('fa-file-code-o');
 
     $content = array();
 
     $follow  = $request->getStr('follow');
     if ($follow) {
       $notice = new PHUIInfoView();
       $notice->setSeverity(PHUIInfoView::SEVERITY_WARNING);
       $notice->setTitle(pht('Unable to Continue'));
       switch ($follow) {
         case 'first':
           $notice->appendChild(
             pht(
               'Unable to continue tracing the history of this file because '.
               'this commit is the first commit in the repository.'));
           break;
         case 'created':
           $notice->appendChild(
             pht(
               'Unable to continue tracing the history of this file because '.
               'this commit created the file.'));
           break;
       }
       $content[] = $notice;
     }
 
     $renamed = $request->getStr('renamed');
     if ($renamed) {
       $notice = new PHUIInfoView();
       $notice->setSeverity(PHUIInfoView::SEVERITY_NOTICE);
       $notice->setTitle(pht('File Renamed'));
       $notice->appendChild(
         pht(
           'File history passes through a rename from "%s" to "%s".',
           $drequest->getPath(),
           $renamed));
       $content[] = $notice;
     }
 
     $content[] = $corpus;
     $content[] = $this->buildOpenRevisions();
 
     $crumbs = $this->buildCrumbs(
       array(
         'branch' => true,
         'path'   => true,
         'view'   => 'browse',
       ));
     $crumbs->setBorder(true);
 
     $basename = basename($this->getDiffusionRequest()->getPath());
 
     $view = id(new PHUITwoColumnView())
       ->setHeader($header)
       ->setCurtain($curtain)
       ->setMainColumn(array(
         $content,
         ));
 
     if ($properties) {
       $view->addPropertySection(pht('Details'), $properties);
     }
 
     $title = array($basename, $repository->getDisplayName());
 
     return $this->newPage()
       ->setTitle($title)
       ->setCrumbs($crumbs)
       ->appendChild(
         array(
           $view,
       ));
 
   }
 
   public function browseDirectory(
     DiffusionBrowseResultSet $results,
     PHUIPagerView $pager) {
 
     $request = $this->getRequest();
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     $reason = $results->getReasonForEmptyResultSet();
 
     $curtain = $this->buildCurtain($drequest);
     $details = $this->buildPropertyView($drequest);
 
     $header = $this->buildHeaderView($drequest);
     $header->setHeaderIcon('fa-folder-open');
 
     $search_form = $this->renderSearchForm();
 
     $empty_result = null;
     $browse_panel = null;
     if (!$results->isValidResults()) {
       $empty_result = new DiffusionEmptyResultView();
       $empty_result->setDiffusionRequest($drequest);
       $empty_result->setDiffusionBrowseResultSet($results);
       $empty_result->setView($request->getStr('view'));
     } else {
       $phids = array();
       foreach ($results->getPaths() as $result) {
         $data = $result->getLastCommitData();
         if ($data) {
           if ($data->getCommitDetail('authorPHID')) {
             $phids[$data->getCommitDetail('authorPHID')] = true;
           }
         }
       }
 
       $phids = array_keys($phids);
       $handles = $this->loadViewerHandles($phids);
 
       $browse_table = id(new DiffusionBrowseTableView())
         ->setDiffusionRequest($drequest)
         ->setHandles($handles)
         ->setPaths($results->getPaths())
         ->setUser($request->getUser());
 
       $browse_header = id(new PHUIHeaderView())
         ->setHeader(nonempty(basename($drequest->getPath()), '/'))
         ->setHeaderIcon('fa-folder-open');
 
       $browse_panel = id(new PHUIObjectBoxView())
         ->setHeader($browse_header)
         ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
         ->setTable($browse_table);
 
       $browse_panel->setShowHide(
         array(pht('Show Search')),
         pht('Hide Search'),
         $search_form,
         '#');
     }
 
     $open_revisions = $this->buildOpenRevisions();
     $readme = $this->renderDirectoryReadme($results);
 
     $crumbs = $this->buildCrumbs(
       array(
         'branch' => true,
         'path'   => true,
         'view'   => 'browse',
       ));
 
     $pager_box = $this->renderTablePagerBox($pager);
     $crumbs->setBorder(true);
 
     $view = id(new PHUITwoColumnView())
       ->setHeader($header)
       ->setCurtain($curtain)
       ->setMainColumn(array(
         $empty_result,
         $browse_panel,
       ))
       ->setFooter(array(
           $open_revisions,
           $readme,
           $pager_box,
       ));
 
     if ($details) {
       $view->addPropertySection(pht('Details'), $details);
     }
 
     return $this->newPage()
       ->setTitle(array(
           nonempty(basename($drequest->getPath()), '/'),
           $repository->getDisplayName(),
         ))
       ->setCrumbs($crumbs)
       ->appendChild(
         array(
           $view,
         ));
   }
 
   private function renderSearchResults() {
     $request = $this->getRequest();
 
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
     $results = array();
 
     $pager = id(new PHUIPagerView())
       ->readFromRequest($request);
 
     $search_mode = null;
     switch ($repository->getVersionControlSystem()) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         $results = array();
         break;
       default:
         if (strlen($this->getRequest()->getStr('grep'))) {
           $search_mode = 'grep';
           $query_string = $request->getStr('grep');
           $results = $this->callConduitWithDiffusionRequest(
             'diffusion.searchquery',
             array(
               'grep' => $query_string,
               'commit' => $drequest->getStableCommit(),
               'path' => $drequest->getPath(),
               'limit' => $pager->getPageSize() + 1,
               'offset' => $pager->getOffset(),
             ));
         } else { // Filename search.
           $search_mode = 'find';
           $query_string = $request->getStr('find');
           $results = $this->callConduitWithDiffusionRequest(
             'diffusion.querypaths',
             array(
               'pattern' => $query_string,
               'commit' => $drequest->getStableCommit(),
               'path' => $drequest->getPath(),
               'limit' => $pager->getPageSize() + 1,
               'offset' => $pager->getOffset(),
             ));
         }
         break;
     }
     $results = $pager->sliceResults($results);
 
     if ($search_mode == 'grep') {
       $table = $this->renderGrepResults($results, $query_string);
       $header = pht(
         'File content matching "%s" under "%s"',
         $query_string,
         nonempty($drequest->getPath(), '/'));
     } else {
       $table = $this->renderFindResults($results);
       $header = pht(
         'Paths matching "%s" under "%s"',
         $query_string,
         nonempty($drequest->getPath(), '/'));
     }
 
     $box = id(new PHUIObjectBoxView())
       ->setHeaderText($header)
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->setTable($table);
 
     $pager_box = $this->renderTablePagerBox($pager);
 
     return array($box, $pager_box);
   }
 
   private function renderGrepResults(array $results, $pattern) {
     $drequest = $this->getDiffusionRequest();
 
     require_celerity_resource('phabricator-search-results-css');
 
     $rows = array();
     foreach ($results as $result) {
       list($path, $line, $string) = $result;
 
       $href = $drequest->generateURI(array(
         'action' => 'browse',
         'path' => $path,
         'line' => $line,
       ));
 
       $matches = null;
       $count = @preg_match_all(
         '('.$pattern.')u',
         $string,
         $matches,
         PREG_OFFSET_CAPTURE);
 
       if (!$count) {
         $output = ltrim($string);
       } else {
         $output = array();
         $cursor = 0;
         $length = strlen($string);
         foreach ($matches[0] as $match) {
           $offset = $match[1];
           if ($cursor != $offset) {
             $output[] = array(
               'text' => substr($string, $cursor, $offset),
               'highlight' => false,
             );
           }
           $output[] = array(
             'text' => $match[0],
             'highlight' => true,
           );
           $cursor = $offset + strlen($match[0]);
         }
         if ($cursor != $length) {
           $output[] = array(
             'text' => substr($string, $cursor),
             'highlight' => false,
           );
         }
 
         if ($output) {
           $output[0]['text'] =  ltrim($output[0]['text']);
         }
 
         foreach ($output as $key => $segment) {
           if ($segment['highlight']) {
             $output[$key] = phutil_tag('strong', array(), $segment['text']);
           } else {
             $output[$key] = $segment['text'];
           }
         }
       }
 
       $string = phutil_tag(
         'pre',
         array('class' => 'PhabricatorMonospaced phui-source-fragment'),
         $output);
 
       $path = Filesystem::readablePath($path, $drequest->getPath());
 
       $rows[] = array(
         phutil_tag('a', array('href' => $href), $path),
         $line,
         $string,
       );
     }
 
     $table = id(new AphrontTableView($rows))
       ->setClassName('remarkup-code')
       ->setHeaders(array(pht('Path'), pht('Line'), pht('String')))
       ->setColumnClasses(array('', 'n', 'wide'))
       ->setNoDataString(
         pht(
           'The pattern you searched for was not found in the content of any '.
           'files.'));
 
     return $table;
   }
 
   private function renderFindResults(array $results) {
     $drequest = $this->getDiffusionRequest();
 
     $rows = array();
     foreach ($results as $result) {
       $href = $drequest->generateURI(array(
         'action' => 'browse',
         'path' => $result,
       ));
 
       $readable = Filesystem::readablePath($result, $drequest->getPath());
 
       $rows[] = array(
         phutil_tag('a', array('href' => $href), $readable),
       );
     }
 
     $table = id(new AphrontTableView($rows))
       ->setHeaders(array(pht('Path')))
       ->setColumnClasses(array('wide'))
       ->setNoDataString(
         pht(
           'The pattern you searched for did not match the names of any '.
           'files.'));
 
     return $table;
   }
 
   private function loadLintMessages() {
     $drequest = $this->getDiffusionRequest();
     $branch = $drequest->loadBranch();
 
     if (!$branch || !$branch->getLintCommit()) {
       return;
     }
 
     $this->lintCommit = $branch->getLintCommit();
 
     $conn = id(new PhabricatorRepository())->establishConnection('r');
 
     $where = '';
     if ($drequest->getLint()) {
       $where = qsprintf(
         $conn,
         'AND code = %s',
         $drequest->getLint());
     }
 
     $this->lintMessages = queryfx_all(
       $conn,
       'SELECT * FROM %T WHERE branchID = %d %Q AND path = %s',
       PhabricatorRepository::TABLE_LINTMESSAGE,
       $branch->getID(),
       $where,
       '/'.$drequest->getPath());
   }
 
   private function buildCorpus(
     $show_blame,
     $file_corpus,
     $needs_blame,
     DiffusionRequest $drequest,
     $path,
     $data) {
 
     $viewer = $this->getViewer();
     $blame_timeout = 15;
     $blame_failed = false;
 
     $highlight_limit = DifferentialChangesetParser::HIGHLIGHT_BYTE_LIMIT;
     $blame_limit = DifferentialChangesetParser::HIGHLIGHT_BYTE_LIMIT;
     $can_highlight = (strlen($file_corpus) <= $highlight_limit);
     $can_blame = (strlen($file_corpus) <= $blame_limit);
 
     if ($needs_blame && $can_blame) {
       $blame = $this->loadBlame($path, $drequest->getCommit(), $blame_timeout);
       list($blame_list, $blame_commits) = $blame;
       if ($blame_list === null) {
         $blame_failed = true;
         $blame_list = array();
       }
     } else {
       $blame_list = array();
       $blame_commits = array();
     }
 
     require_celerity_resource('syntax-highlighting-css');
     if ($can_highlight) {
       $highlighted = PhabricatorSyntaxHighlighter::highlightWithFilename(
         $path,
         $file_corpus);
     } else {
       // Highlight as plain text to escape the content properly.
       $highlighted = PhabricatorSyntaxHighlighter::highlightWithLanguage(
         'txt',
         $file_corpus);
     }
 
     $lines = phutil_split_lines($highlighted);
 
     $rows = $this->buildDisplayRows(
       $lines,
       $blame_list,
       $blame_commits,
       $show_blame);
 
     $corpus_table = javelin_tag(
       'table',
       array(
         'class' => 'diffusion-source remarkup-code PhabricatorMonospaced',
         'sigil' => 'phabricator-source',
       ),
       $rows);
 
     if ($this->getRequest()->isAjax()) {
       return $corpus_table;
     }
 
     $id = celerity_generate_unique_node_id();
 
     $repo = $drequest->getRepository();
     $symbol_repos = nonempty($repo->getSymbolSources(), array());
     $symbol_repos[] = $repo->getPHID();
 
     $lang = last(explode('.', $drequest->getPath()));
     $repo_languages = $repo->getSymbolLanguages();
     $repo_languages = nonempty($repo_languages, array());
     $repo_languages = array_fill_keys($repo_languages, true);
 
     $needs_symbols = true;
     if ($repo_languages && $symbol_repos) {
       $have_symbols = id(new DiffusionSymbolQuery())
           ->existsSymbolsInRepository($repo->getPHID());
       if (!$have_symbols) {
         $needs_symbols = false;
       }
     }
 
     if ($needs_symbols && $repo_languages) {
       $needs_symbols = isset($repo_languages[$lang]);
     }
 
     if ($needs_symbols) {
       Javelin::initBehavior(
         'repository-crossreference',
         array(
           'container' => $id,
           'lang' => $lang,
           'repositories' => $symbol_repos,
         ));
     }
 
     $corpus = phutil_tag(
       'div',
       array(
         'id' => $id,
       ),
       $corpus_table);
 
     Javelin::initBehavior('load-blame', array('id' => $id));
 
 
     $edit = $this->renderEditButton();
     $file = $this->renderFileButton();
     $header = id(new PHUIHeaderView())
       ->setHeader(basename($this->getDiffusionRequest()->getPath()))
       ->setHeaderIcon('fa-file-code-o')
       ->addActionLink($edit)
       ->addActionLink($file);
 
     $corpus = id(new PHUIObjectBoxView())
       ->setHeader($header)
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->appendChild($corpus)
       ->setCollapsed(true);
 
     $messages = array();
 
     if (!$can_highlight) {
       $messages[] = pht(
         'This file is larger than %s, so syntax highlighting is disabled '.
         'by default.',
         phutil_format_bytes($highlight_limit));
     }
 
     if ($show_blame && !$can_blame) {
       $messages[] = pht(
         'This file is larger than %s, so blame is disabled.',
         phutil_format_bytes($blame_limit));
     }
 
     if ($blame_failed) {
       $messages[] = pht(
         'Failed to load blame information for this file in %s second(s).',
         new PhutilNumber($blame_timeout));
     }
 
     if ($messages) {
       $corpus->setInfoView(
         id(new PHUIInfoView())
           ->setSeverity(PHUIInfoView::SEVERITY_WARNING)
           ->setErrors($messages));
     }
 
     return $corpus;
   }
 
   private function enrichCurtain(
     PHUICurtainView $curtain,
     DiffusionRequest $drequest,
     $show_blame) {
 
     $viewer = $this->getViewer();
     $base_uri = $this->getRequest()->getRequestURI();
 
     $curtain->addAction(
       id(new PhabricatorActionView())
         ->setName(pht('Show Last Change'))
         ->setHref(
           $drequest->generateURI(
             array(
               'action' => 'change',
             )))
         ->setIcon('fa-backward'));
 
     if ($show_blame) {
       $blame_text = pht('Disable Blame');
       $blame_icon = 'fa-exclamation-circle lightgreytext';
       $blame_value = 0;
     } else {
       $blame_text = pht('Enable Blame');
       $blame_icon = 'fa-exclamation-circle';
       $blame_value = 1;
     }
 
     $curtain->addAction(
       id(new PhabricatorActionView())
         ->setName($blame_text)
         ->setHref($base_uri->alter('blame', $blame_value))
         ->setIcon($blame_icon)
         ->setUser($viewer)
         ->setRenderAsForm($viewer->isLoggedIn()));
 
     $href = null;
     if ($this->getRequest()->getStr('lint') !== null) {
       $lint_text = pht('Hide %d Lint Message(s)', count($this->lintMessages));
       $href = $base_uri->alter('lint', null);
 
     } else if ($this->lintCommit === null) {
       $lint_text = pht('Lint not Available');
     } else {
       $lint_text = pht(
         'Show %d Lint Message(s)',
         count($this->lintMessages));
       $href = $this->getDiffusionRequest()->generateURI(array(
         'action' => 'browse',
         'commit' => $this->lintCommit,
       ))->alter('lint', '');
     }
 
     $curtain->addAction(
       id(new PhabricatorActionView())
         ->setName($lint_text)
         ->setHref($href)
         ->setIcon('fa-exclamation-triangle')
         ->setDisabled(!$href));
 
 
     $repository = $drequest->getRepository();
 
     $owners = 'PhabricatorOwnersApplication';
     if (PhabricatorApplication::isClassInstalled($owners)) {
       $package_query = id(new PhabricatorOwnersPackageQuery())
         ->setViewer($viewer)
         ->withStatuses(array(PhabricatorOwnersPackage::STATUS_ACTIVE))
         ->withControl(
           $repository->getPHID(),
           array(
             $drequest->getPath(),
           ));
 
       $package_query->execute();
 
       $packages = $package_query->getControllingPackagesForPath(
         $repository->getPHID(),
         $drequest->getPath());
 
       if ($packages) {
         $ownership = id(new PHUIStatusListView())
           ->setUser($viewer);
 
         foreach ($packages as $package) {
           $icon = 'fa-list-alt';
           $color = 'grey';
 
           $item = id(new PHUIStatusItemView())
             ->setIcon($icon, $color)
             ->setTarget($viewer->renderHandle($package->getPHID()));
 
           $ownership->addItem($item);
         }
       } else {
         $ownership = phutil_tag('em', array(), pht('None'));
       }
 
       $curtain->newPanel()
         ->setHeaderText(pht('Owners'))
         ->appendChild($ownership);
     }
 
     return $curtain;
   }
 
   private function renderEditButton() {
     $request = $this->getRequest();
     $user = $request->getUser();
 
     $drequest = $this->getDiffusionRequest();
 
     $repository = $drequest->getRepository();
     $path = $drequest->getPath();
     $line = nonempty((int)$drequest->getLine(), 1);
 
     $editor_link = $user->loadEditorLink($path, $line, $repository);
     $template = $user->loadEditorLink($path, '%l', $repository);
 
     $button = id(new PHUIButtonView())
       ->setTag('a')
       ->setText(pht('Open in Editor'))
       ->setHref($editor_link)
       ->setIcon('fa-pencil')
       ->setID('editor_link')
       ->setMetadata(array('link_template' => $template))
       ->setDisabled(!$editor_link);
 
     return $button;
   }
 
   private function renderFileButton($file_uri = null, $label = null) {
 
     $base_uri = $this->getRequest()->getRequestURI();
 
     if ($file_uri) {
       $text = pht('Download Raw File');
       $href = $file_uri;
       $icon = 'fa-download';
     } else {
       $text = pht('View Raw File');
       $href = $base_uri->alter('view', 'raw');
       $icon = 'fa-file-text';
     }
 
     if ($label !== null) {
       $text = $label;
     }
 
     $button = id(new PHUIButtonView())
       ->setTag('a')
       ->setText($text)
       ->setHref($href)
       ->setIcon($icon);
 
     return $button;
   }
 
   private function renderGitLFSButton() {
     $viewer = $this->getViewer();
 
     $uri = $this->getRequest()->getRequestURI();
     $href = $uri->alter('view', 'git-lfs');
 
     $text = pht('Download from Git LFS');
     $icon = 'fa-download';
 
     return id(new PHUIButtonView())
       ->setTag('a')
       ->setText($text)
       ->setHref($href)
       ->setIcon($icon);
   }
 
   private function buildDisplayRows(
     array $lines,
     array $blame_list,
     array $blame_commits,
     $show_blame) {
 
     $request = $this->getRequest();
     $viewer = $this->getViewer();
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     $revision_map = array();
     $revisions = array();
     if ($blame_commits) {
       $commit_map = mpull($blame_commits, 'getCommitIdentifier', 'getPHID');
 
       $revision_ids = id(new DifferentialRevision())
         ->loadIDsByCommitPHIDs(array_keys($commit_map));
       if ($revision_ids) {
         $revisions = id(new DifferentialRevisionQuery())
           ->setViewer($viewer)
           ->withIDs($revision_ids)
           ->execute();
         $revisions = mpull($revisions, null, 'getID');
       }
 
       foreach ($revision_ids as $commit_phid => $revision_id) {
         $revision_map[$commit_map[$commit_phid]] = $revision_id;
       }
     }
 
     $phids = array();
     foreach ($blame_commits as $commit) {
       $author_phid = $commit->getAuthorPHID();
       if ($author_phid === null) {
         continue;
       }
       $phids[$author_phid] = $author_phid;
     }
 
     foreach ($revisions as $revision) {
       $author_phid = $revision->getAuthorPHID();
       if ($author_phid === null) {
         continue;
       }
       $phids[$author_phid] = $author_phid;
     }
 
     $handles = $viewer->loadHandles($phids);
 
     $colors = array();
     if ($blame_commits) {
       $epochs = array();
 
       foreach ($blame_commits as $identifier => $commit) {
         $epochs[$identifier] = $commit->getEpoch();
       }
 
       $epoch_list = array_filter($epochs);
       $epoch_list = array_unique($epoch_list);
       $epoch_list = array_values($epoch_list);
 
       $epoch_min   = min($epoch_list);
       $epoch_max   = max($epoch_list);
       $epoch_range = ($epoch_max - $epoch_min) + 1;
 
       foreach ($blame_commits as $identifier => $commit) {
         $epoch = $epochs[$identifier];
         if (!$epoch) {
           $color = '#ffffdd'; // Warning color, missing data.
         } else {
           $color_ratio = ($epoch - $epoch_min) / $epoch_range;
           $color_value = 0xE6 * (1.0 - $color_ratio);
           $color = sprintf(
             '#%02x%02x%02x',
             $color_value,
             0xF6,
             $color_value);
         }
 
         $colors[$identifier] = $color;
       }
     }
 
     $display = array();
     $last_identifier = null;
     $last_color = null;
     foreach ($lines as $line_index => $line) {
       $color = '#f6f6f6';
       $duplicate = false;
       if (isset($blame_list[$line_index])) {
         $identifier = $blame_list[$line_index];
         if (isset($colors[$identifier])) {
           $color = $colors[$identifier];
         }
 
         if ($identifier === $last_identifier) {
           $duplicate = true;
         } else {
           $last_identifier = $identifier;
         }
       }
 
       $display[$line_index] = array(
         'data' => $line,
         'target' => false,
         'highlighted' => false,
         'color' => $color,
         'duplicate' => $duplicate,
       );
     }
 
     $line_arr = array();
     $line_str = $drequest->getLine();
     $ranges = explode(',', $line_str);
     foreach ($ranges as $range) {
       if (strpos($range, '-') !== false) {
         list($min, $max) = explode('-', $range, 2);
         $line_arr[] = array(
           'min' => min($min, $max),
           'max' => max($min, $max),
         );
       } else if (strlen($range)) {
         $line_arr[] = array(
           'min' => $range,
           'max' => $range,
         );
       }
     }
 
     // Mark the first highlighted line as the target line.
     if ($line_arr) {
       $target_line = $line_arr[0]['min'];
       if (isset($display[$target_line - 1])) {
         $display[$target_line - 1]['target'] = true;
       }
     }
 
     // Mark all other highlighted lines as highlighted.
     foreach ($line_arr as $range) {
       for ($ii = $range['min']; $ii <= $range['max']; $ii++) {
         if (isset($display[$ii - 1])) {
           $display[$ii - 1]['highlighted'] = true;
         }
       }
     }
 
     $engine = null;
     $inlines = array();
     if ($this->getRequest()->getStr('lint') !== null && $this->lintMessages) {
       $engine = new PhabricatorMarkupEngine();
       $engine->setViewer($viewer);
 
       foreach ($this->lintMessages as $message) {
         $inline = id(new PhabricatorAuditInlineComment())
           ->setSyntheticAuthor(
             ArcanistLintSeverity::getStringForSeverity($message['severity']).
             ' '.$message['code'].' ('.$message['name'].')')
           ->setLineNumber($message['line'])
           ->setContent($message['description']);
         $inlines[$message['line']][] = $inline;
 
         $engine->addObject(
           $inline,
           PhabricatorInlineCommentInterface::MARKUP_FIELD_BODY);
       }
 
       $engine->process();
       require_celerity_resource('differential-changeset-view-css');
     }
 
     $rows = $this->renderInlines(
       idx($inlines, 0, array()),
       $show_blame,
       (bool)$this->coverage,
       $engine);
 
     // NOTE: We're doing this manually because rendering is otherwise
     // dominated by URI generation for very large files.
     $line_base = (string)$drequest->generateURI(
       array(
         'action'  => 'browse',
         'stable'  => true,
       ));
 
     require_celerity_resource('aphront-tooltip-css');
     Javelin::initBehavior('phabricator-oncopy');
     Javelin::initBehavior('phabricator-tooltips');
     Javelin::initBehavior('phabricator-line-linker');
 
     // Render these once, since they tend to get repeated many times in large
     // blame outputs.
     $commit_links = $this->renderCommitLinks($blame_commits, $handles);
     $revision_links = $this->renderRevisionLinks($revisions, $handles);
 
     if ($this->coverage) {
       require_celerity_resource('differential-changeset-view-css');
       Javelin::initBehavior(
         'diffusion-browse-file',
         array(
           'labels' => array(
             'cov-C' => pht('Covered'),
             'cov-N' => pht('Not Covered'),
             'cov-U' => pht('Not Executable'),
           ),
         ));
     }
 
     $skip_text = pht('Skip Past This Commit');
     foreach ($display as $line_index => $line) {
       $row = array();
 
       $line_number = $line_index + 1;
       $line_href = $line_base.'$'.$line_number;
 
       if (isset($blame_list[$line_index])) {
         $identifier = $blame_list[$line_index];
       } else {
         $identifier = null;
       }
 
       $revision_link = null;
       $commit_link = null;
       $before_link = null;
 
       $style = 'background: '.$line['color'].';';
 
       if ($identifier && !$line['duplicate']) {
         if (isset($commit_links[$identifier])) {
           $commit_link = $commit_links[$identifier];
         }
 
         if (isset($revision_map[$identifier])) {
           $revision_id = $revision_map[$identifier];
           if (isset($revision_links[$revision_id])) {
             $revision_link = $revision_links[$revision_id];
           }
         }
 
         $skip_href = $line_href.'?before='.$identifier.'&view=blame';
         $before_link = javelin_tag(
           'a',
           array(
             'href'  => $skip_href,
             'sigil' => 'has-tooltip',
             'meta'  => array(
               'tip'     => $skip_text,
               'align'   => 'E',
               'size'    => 300,
             ),
           ),
           "\xC2\xAB");
       }
 
       if ($show_blame) {
         $row[] = phutil_tag(
           'th',
           array(
             'class' => 'diffusion-blame-link',
           ),
           $before_link);
 
         $object_links = array();
         $object_links[] = $commit_link;
         if ($revision_link) {
           $object_links[] = phutil_tag('span', array(), '/');
           $object_links[] = $revision_link;
         }
 
         $row[] = phutil_tag(
           'th',
           array(
             'class' => 'diffusion-rev-link',
           ),
           $object_links);
       }
 
       $line_link = phutil_tag(
         'a',
         array(
           'href' => $line_href,
           'style' => $style,
         ),
         $line_number);
 
       $row[] = javelin_tag(
         'th',
         array(
           'class' => 'diffusion-line-link',
           'sigil' => 'phabricator-source-line',
           'style' => $style,
         ),
         $line_link);
 
       if ($line['target']) {
         Javelin::initBehavior(
           'diffusion-jump-to',
           array(
             'target' => 'scroll_target',
           ));
         $anchor_text = phutil_tag(
           'a',
           array(
             'id' => 'scroll_target',
           ),
           '');
       } else {
         $anchor_text = null;
       }
 
       $row[] = phutil_tag(
         'td',
         array(
         ),
         array(
           $anchor_text,
 
           // NOTE: See phabricator-oncopy behavior.
           "\xE2\x80\x8B",
 
           // TODO: [HTML] Not ideal.
           phutil_safe_html(str_replace("\t", '  ', $line['data'])),
         ));
 
       if ($this->coverage) {
         $cov_index = $line_index;
 
         if (isset($this->coverage[$cov_index])) {
           $cov_class = $this->coverage[$cov_index];
         } else {
           $cov_class = 'N';
         }
 
         $row[] = phutil_tag(
           'td',
           array(
             'class' => 'cov cov-'.$cov_class,
           ),
           '');
       }
 
       $rows[] = phutil_tag(
         'tr',
         array(
           'class' => ($line['highlighted'] ?
                       'phabricator-source-highlight' :
                       null),
         ),
         $row);
 
       $cur_inlines = $this->renderInlines(
         idx($inlines, $line_number, array()),
         $show_blame,
         $this->coverage,
         $engine);
       foreach ($cur_inlines as $cur_inline) {
         $rows[] = $cur_inline;
       }
     }
 
     return $rows;
   }
 
   private function renderInlines(
     array $inlines,
     $show_blame,
     $has_coverage,
     $engine) {
 
     $rows = array();
     foreach ($inlines as $inline) {
 
       // TODO: This should use modern scaffolding code.
 
       $inline_view = id(new PHUIDiffInlineCommentDetailView())
         ->setUser($this->getViewer())
         ->setMarkupEngine($engine)
         ->setInlineComment($inline)
         ->render();
 
       $row = array_fill(0, ($show_blame ? 3 : 1), phutil_tag('th'));
 
       $row[] = phutil_tag('td', array(), $inline_view);
 
       if ($has_coverage) {
         $row[] = phutil_tag(
           'td',
           array(
             'class' => 'cov cov-I',
           ));
       }
 
       $rows[] = phutil_tag('tr', array('class' => 'inline'), $row);
     }
 
     return $rows;
   }
 
   private function buildImageCorpus($file_uri) {
     $properties = new PHUIPropertyListView();
 
     $properties->addImageContent(
       phutil_tag(
         'img',
         array(
           'src' => $file_uri,
         )));
 
     $file = $this->renderFileButton($file_uri);
     $header = id(new PHUIHeaderView())
       ->setHeader(basename($this->getDiffusionRequest()->getPath()))
       ->addActionLink($file)
       ->setHeaderIcon('fa-file-image-o');
 
     return id(new PHUIObjectBoxView())
       ->setHeader($header)
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->addPropertyList($properties);
   }
 
   private function buildBinaryCorpus($file_uri, $data) {
     $size = new PhutilNumber(strlen($data));
     $text = pht('This is a binary file. It is %s byte(s) in length.', $size);
     $text = id(new PHUIBoxView())
       ->addPadding(PHUI::PADDING_LARGE)
       ->appendChild($text);
 
     $file = $this->renderFileButton($file_uri);
     $header = id(new PHUIHeaderView())
       ->setHeader(pht('Details'))
       ->addActionLink($file);
 
     $box = id(new PHUIObjectBoxView())
       ->setHeader($header)
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->appendChild($text);
 
     return $box;
   }
 
   private function buildErrorCorpus($message) {
     $text = id(new PHUIBoxView())
       ->addPadding(PHUI::PADDING_LARGE)
       ->appendChild($message);
 
     $header = id(new PHUIHeaderView())
       ->setHeader(pht('Details'));
 
     $box = id(new PHUIObjectBoxView())
       ->setHeader($header)
       ->appendChild($text);
 
     return $box;
   }
 
   private function buildBeforeResponse($before) {
     $request = $this->getRequest();
     $drequest = $this->getDiffusionRequest();
 
     // NOTE: We need to get the grandparent so we can capture filename changes
     // in the parent.
 
     $parent = $this->loadParentCommitOf($before);
     $old_filename = null;
     $was_created = false;
     if ($parent) {
       $grandparent = $this->loadParentCommitOf($parent);
 
       if ($grandparent) {
         $rename_query = new DiffusionRenameHistoryQuery();
         $rename_query->setRequest($drequest);
         $rename_query->setOldCommit($grandparent);
         $rename_query->setViewer($request->getUser());
         $old_filename = $rename_query->loadOldFilename();
         $was_created = $rename_query->getWasCreated();
       }
     }
 
     $follow = null;
     if ($was_created) {
       // If the file was created in history, that means older commits won't
       // have it. Since we know it existed at 'before', it must have been
       // created then; jump there.
       $target_commit = $before;
       $follow = 'created';
     } else if ($parent) {
       // If we found a parent, jump to it. This is the normal case.
       $target_commit = $parent;
     } else {
       // If there's no parent, this was probably created in the initial commit?
       // And the "was_created" check will fail because we can't identify the
       // grandparent. Keep the user at 'before'.
       $target_commit = $before;
       $follow = 'first';
     }
 
     $path = $drequest->getPath();
     $renamed = null;
     if ($old_filename !== null &&
         $old_filename !== '/'.$path) {
       $renamed = $path;
       $path = $old_filename;
     }
 
     $line = null;
     // If there's a follow error, drop the line so the user sees the message.
     if (!$follow) {
       $line = $this->getBeforeLineNumber($target_commit);
     }
 
     $before_uri = $drequest->generateURI(
       array(
         'action'    => 'browse',
         'commit'    => $target_commit,
         'line'      => $line,
         'path'      => $path,
       ));
 
     $before_uri->setQueryParams($request->getRequestURI()->getQueryParams());
     $before_uri = $before_uri->alter('before', null);
     $before_uri = $before_uri->alter('renamed', $renamed);
     $before_uri = $before_uri->alter('follow', $follow);
 
     return id(new AphrontRedirectResponse())->setURI($before_uri);
   }
 
   private function getBeforeLineNumber($target_commit) {
     $drequest = $this->getDiffusionRequest();
     $viewer = $this->getViewer();
 
     $line = $drequest->getLine();
     if (!$line) {
       return null;
     }
 
     $diff_info = $this->callConduitWithDiffusionRequest(
       'diffusion.rawdiffquery',
       array(
         'commit' => $drequest->getCommit(),
         'path' => $drequest->getPath(),
         'againstCommit' => $target_commit,
       ));
 
     $file_phid = $diff_info['filePHID'];
     $file = id(new PhabricatorFileQuery())
       ->setViewer($viewer)
       ->withPHIDs(array($file_phid))
       ->executeOne();
     if (!$file) {
       throw new Exception(
         pht(
           'Failed to load file ("%s") returned by "%s".',
           $file_phid,
           'diffusion.rawdiffquery.'));
     }
 
     $raw_diff = $file->loadFileData();
 
     $old_line = 0;
     $new_line = 0;
 
     foreach (explode("\n", $raw_diff) as $text) {
       if ($text[0] == '-' || $text[0] == ' ') {
         $old_line++;
       }
       if ($text[0] == '+' || $text[0] == ' ') {
         $new_line++;
       }
       if ($new_line == $line) {
         return $old_line;
       }
     }
 
     // We didn't find the target line.
     return $line;
   }
 
   private function loadParentCommitOf($commit) {
     $drequest = $this->getDiffusionRequest();
     $user = $this->getRequest()->getUser();
 
     $before_req = DiffusionRequest::newFromDictionary(
       array(
         'user' => $user,
         'repository' => $drequest->getRepository(),
         'commit' => $commit,
       ));
 
     $parents = DiffusionQuery::callConduitWithDiffusionRequest(
       $user,
       $before_req,
       'diffusion.commitparentsquery',
       array(
         'commit' => $commit,
       ));
 
     return head($parents);
   }
 
   private function renderRevisionTooltip(
     DifferentialRevision $revision,
     $handles) {
     $viewer = $this->getRequest()->getUser();
 
     $date = phabricator_date($revision->getDateModified(), $viewer);
     $id = $revision->getID();
     $title = $revision->getTitle();
     $header = "D{$id} {$title}";
 
     $author = $handles[$revision->getAuthorPHID()]->getName();
 
     return "{$header}\n{$date} \xC2\xB7 {$author}";
   }
 
   private function renderCommitTooltip(
     PhabricatorRepositoryCommit $commit,
     $author) {
 
     $viewer = $this->getRequest()->getUser();
 
     $date = phabricator_date($commit->getEpoch(), $viewer);
     $summary = trim($commit->getSummary());
 
     return "{$summary}\n{$date} \xC2\xB7 {$author}";
   }
 
   protected function renderSearchForm() {
     $drequest = $this->getDiffusionRequest();
 
     $forms = array();
     $form = id(new AphrontFormView())
       ->setUser($this->getViewer())
       ->setMethod('GET');
 
     switch ($drequest->getRepository()->getVersionControlSystem()) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         $forms[] = id(clone $form)
           ->appendChild(pht('Search is not available in Subversion.'));
         break;
       default:
         $forms[] = id(clone $form)
           ->appendChild(
             id(new AphrontFormTextWithSubmitControl())
               ->setLabel(pht('File Name'))
               ->setSubmitLabel(pht('Search File Names'))
               ->setName('find')
               ->setValue($this->getRequest()->getStr('find')));
         $forms[] = id(clone $form)
           ->appendChild(
             id(new AphrontFormTextWithSubmitControl())
               ->setLabel(pht('Pattern'))
               ->setSubmitLabel(pht('Grep File Content'))
               ->setName('grep')
               ->setValue($this->getRequest()->getStr('grep')));
         break;
     }
 
     require_celerity_resource('diffusion-icons-css');
     $form_box = phutil_tag_div('diffusion-search-boxen', $forms);
 
     return $form_box;
   }
 
   protected function markupText($text) {
     $engine = PhabricatorMarkupEngine::newDiffusionMarkupEngine();
     $engine->setConfig('viewer', $this->getRequest()->getUser());
     $text = $engine->markupText($text);
 
     $text = phutil_tag(
       'div',
       array(
         'class' => 'phabricator-remarkup',
       ),
       $text);
 
     return $text;
   }
 
   protected function buildHeaderView(DiffusionRequest $drequest) {
     $viewer = $this->getViewer();
 
     $tag = $this->renderCommitHashTag($drequest);
 
     $header = id(new PHUIHeaderView())
       ->setUser($viewer)
       ->setHeader($this->renderPathLinks($drequest, $mode = 'browse'))
       ->addTag($tag);
 
     return $header;
   }
 
   protected function buildCurtain(DiffusionRequest $drequest) {
     $viewer = $this->getViewer();
+    $repository = $drequest->getRepository();
 
     $curtain = $this->newCurtainView($drequest);
 
     $history_uri = $drequest->generateURI(
       array(
         'action' => 'history',
       ));
 
     $curtain->addAction(
       id(new PhabricatorActionView())
         ->setName(pht('View History'))
         ->setHref($history_uri)
         ->setIcon('fa-list'));
 
     $behind_head = $drequest->getSymbolicCommit();
+
+    if ($repository->supportsBranchComparison()) {
+      $compare_uri = $drequest->generateURI(
+        array(
+          'action' => 'compare',
+        ));
+
+      $curtain->addAction(
+        id(new PhabricatorActionView())
+          ->setName(pht('Compare Against...'))
+          ->setIcon('fa-code-fork')
+          ->setWorkflow(true)
+          ->setHref($compare_uri));
+    }
+
     $head_uri = $drequest->generateURI(
       array(
         'commit' => '',
         'action' => 'browse',
       ));
     $curtain->addAction(
       id(new PhabricatorActionView())
         ->setName(pht('Jump to HEAD'))
         ->setHref($head_uri)
         ->setIcon('fa-home')
         ->setDisabled(!$behind_head));
 
     return $curtain;
   }
 
   protected function buildPropertyView(
     DiffusionRequest $drequest) {
 
     $viewer = $this->getViewer();
     $view = id(new PHUIPropertyListView())
       ->setUser($viewer);
 
     if ($drequest->getSymbolicType() == 'tag') {
       $symbolic = $drequest->getSymbolicCommit();
       $view->addProperty(pht('Tag'), $symbolic);
 
       $tags = $this->callConduitWithDiffusionRequest(
         'diffusion.tagsquery',
         array(
           'names' => array($symbolic),
           'needMessages' => true,
         ));
       $tags = DiffusionRepositoryTag::newFromConduit($tags);
 
       $tags = mpull($tags, null, 'getName');
       $tag = idx($tags, $symbolic);
 
       if ($tag && strlen($tag->getMessage())) {
         $view->addSectionHeader(
           pht('Tag Content'), 'fa-tag');
         $view->addTextContent($this->markupText($tag->getMessage()));
       }
     }
 
     if ($view->hasAnyProperties()) {
       return $view;
     }
 
     return null;
   }
 
   private function buildOpenRevisions() {
     $viewer = $this->getViewer();
 
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
     $path = $drequest->getPath();
 
     $path_map = id(new DiffusionPathIDQuery(array($path)))->loadPathIDs();
     $path_id = idx($path_map, $path);
     if (!$path_id) {
       return null;
     }
 
     $recent = (PhabricatorTime::getNow() - phutil_units('30 days in seconds'));
 
     $revisions = id(new DifferentialRevisionQuery())
       ->setViewer($viewer)
       ->withPath($repository->getID(), $path_id)
       ->withStatus(DifferentialRevisionQuery::STATUS_OPEN)
       ->withUpdatedEpochBetween($recent, null)
       ->setOrder(DifferentialRevisionQuery::ORDER_MODIFIED)
       ->setLimit(10)
       ->needRelationships(true)
       ->needFlags(true)
       ->needDrafts(true)
       ->execute();
 
     if (!$revisions) {
       return null;
     }
 
     $header = id(new PHUIHeaderView())
       ->setHeader(pht('Open Revisions'))
       ->setSubheader(
         pht('Recently updated open revisions affecting this file.'));
 
     $view = id(new DifferentialRevisionListView())
       ->setHeader($header)
       ->setRevisions($revisions)
       ->setUser($viewer);
 
     $phids = $view->getRequiredHandlePHIDs();
     $handles = $this->loadViewerHandles($phids);
     $view->setHandles($handles);
 
     return $view;
   }
 
   private function loadBlame($path, $commit, $timeout) {
     $blame = $this->callConduitWithDiffusionRequest(
       'diffusion.blame',
       array(
         'commit' => $commit,
         'paths' => array($path),
         'timeout' => $timeout,
       ));
 
     $identifiers = idx($blame, $path, null);
 
     if ($identifiers) {
       $viewer = $this->getViewer();
       $drequest = $this->getDiffusionRequest();
       $repository = $drequest->getRepository();
 
       $commits = id(new DiffusionCommitQuery())
         ->setViewer($viewer)
         ->withRepository($repository)
         ->withIdentifiers($identifiers)
         // TODO: We only fetch this to improve author display behavior, but
         // shouldn't really need to?
         ->needCommitData(true)
         ->execute();
       $commits = mpull($commits, null, 'getCommitIdentifier');
     } else {
       $commits = array();
     }
 
     return array($identifiers, $commits);
   }
 
   private function renderCommitLinks(array $commits, $handles) {
     $links = array();
     foreach ($commits as $identifier => $commit) {
       $tooltip = $this->renderCommitTooltip(
         $commit,
         $commit->renderAuthorShortName($handles));
 
       $commit_link = javelin_tag(
         'a',
         array(
           'href' => $commit->getURI(),
           'sigil' => 'has-tooltip',
           'meta'  => array(
             'tip'   => $tooltip,
             'align' => 'E',
             'size'  => 600,
           ),
         ),
         $commit->getLocalName());
 
       $links[$identifier] = $commit_link;
     }
 
     return $links;
   }
 
   private function renderRevisionLinks(array $revisions, $handles) {
     $links = array();
 
     foreach ($revisions as $revision) {
       $revision_id = $revision->getID();
 
       $tooltip = $this->renderRevisionTooltip($revision, $handles);
 
       $revision_link = javelin_tag(
         'a',
         array(
           'href' => '/'.$revision->getMonogram(),
           'sigil' => 'has-tooltip',
           'meta'  => array(
             'tip'   => $tooltip,
             'align' => 'E',
             'size'  => 600,
           ),
         ),
         $revision->getMonogram());
 
       $links[$revision_id] = $revision_link;
     }
 
     return $links;
   }
 
   private function getGitLFSRef(PhabricatorRepository $repository, $data) {
     if (!$repository->canUseGitLFS()) {
       return null;
     }
 
     $lfs_pattern = '(^version https://git-lfs\\.github\\.com/spec/v1[\r\n])';
     if (!preg_match($lfs_pattern, $data)) {
       return null;
     }
 
     $matches = null;
     if (!preg_match('(^oid sha256:(.*)$)m', $data, $matches)) {
       return null;
     }
 
     $hash = $matches[1];
     $hash = trim($hash);
 
     return id(new PhabricatorRepositoryGitLFSRefQuery())
       ->setViewer($this->getViewer())
       ->withRepositoryPHIDs(array($repository->getPHID()))
       ->withObjectHashes(array($hash))
       ->executeOne();
   }
 
   private function buildGitLFSCorpus(PhabricatorRepositoryGitLFSRef $ref) {
     // TODO: We should probably test if we can load the file PHID here and
     // show the user an error if we can't, rather than making them click
     // through to hit an error.
 
     $header = id(new PHUIHeaderView())
       ->setHeader(basename($this->getDiffusionRequest()->getPath()))
       ->setHeaderIcon('fa-archive');
 
     $severity = PHUIInfoView::SEVERITY_NOTICE;
 
     $messages = array();
     $messages[] = pht(
       'This %s file is stored in Git Large File Storage.',
       phutil_format_bytes($ref->getByteSize()));
 
     try {
       $file = $this->loadGitLFSFile($ref);
       $data = $this->renderGitLFSButton();
       $header->addActionLink($data);
     } catch (Exception $ex) {
       $severity = PHUIInfoView::SEVERITY_ERROR;
       $messages[] = pht('The data for this file could not be loaded.');
     }
 
     $raw = $this->renderFileButton(null, pht('View Raw LFS Pointer'));
     $header->addActionLink($raw);
 
     $corpus = id(new PHUIObjectBoxView())
       ->setHeader($header)
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->setCollapsed(true);
 
     if ($messages) {
       $corpus->setInfoView(
         id(new PHUIInfoView())
           ->setSeverity($severity)
           ->setErrors($messages));
     }
 
     return $corpus;
   }
 
   private function loadGitLFSFile(PhabricatorRepositoryGitLFSRef $ref) {
     $viewer = $this->getViewer();
 
     $file = id(new PhabricatorFileQuery())
       ->setViewer($viewer)
       ->withPHIDs(array($ref->getFilePHID()))
       ->executeOne();
     if (!$file) {
       throw new Exception(
         pht(
           'Failed to load file object for Git LFS ref "%s"!',
           $ref->getObjectHash()));
     }
 
     return $file;
   }
 
 
 }
diff --git a/src/applications/diffusion/controller/DiffusionCompareController.php b/src/applications/diffusion/controller/DiffusionCompareController.php
index 3ef16fd497..ab47d21910 100644
--- a/src/applications/diffusion/controller/DiffusionCompareController.php
+++ b/src/applications/diffusion/controller/DiffusionCompareController.php
@@ -1,260 +1,325 @@
 <?php
 
 final class DiffusionCompareController extends DiffusionController {
 
   public function shouldAllowPublic() {
     return true;
   }
 
   public function handleRequest(AphrontRequest $request) {
     $response = $this->loadDiffusionContext();
     if ($response) {
       return $response;
     }
 
     $viewer = $this->getViewer();
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
-    $content = array();
-
-    $crumbs = $this->buildCrumbs(array('view' => 'compare'));
-
-    $empty_title = null;
-    $error_message = null;
-
-    if ($repository->getVersionControlSystem() !=
-          PhabricatorRepositoryType::REPOSITORY_TYPE_GIT) {
-      $empty_title = pht('Not supported');
-      $error_message = pht(
-        'This feature is not yet supported for %s repositories.',
-        $repository->getVersionControlSystem());
-      $content[] = id(new PHUIInfoView())
-        ->setTitle($empty_title)
-        ->setSeverity(PHUIInfoView::SEVERITY_WARNING)
-        ->setErrors(array($error_message));
+    if (!$repository->supportsBranchComparison()) {
+      return $this->newDialog()
+        ->setTitle(pht('Not Supported'))
+        ->appendParagraph(
+          pht(
+            'Branch comparison is not supported for this version control '.
+            'system.'))
+        ->addCancelButton($this->getApplicationURI(), pht('Okay'));
     }
 
     $head_ref = $request->getStr('head');
     $against_ref = $request->getStr('against');
 
-    $refs = id(new DiffusionCachedResolveRefsQuery())
-      ->setRepository($repository)
-      ->withRefs(array($head_ref, $against_ref))
-      ->execute();
+    $must_prompt = false;
+    if (!$request->isFormPost()) {
+      if (!strlen($head_ref)) {
+        $head_ref = $drequest->getSymbolicCommit();
+        if (!strlen($head_ref)) {
+          $head_ref = $drequest->getBranch();
+        }
+      }
 
+      if (!strlen($against_ref)) {
+        $default_branch = $repository->getDefaultBranch();
+        if ($default_branch != $head_ref) {
+          $against_ref = $default_branch;
 
-    if (count($refs) == 2) {
-      $content[] = $this->buildCompareContent($drequest);
-    } else {
-      $content[] = $this->buildCompareForm($request, $refs);
+          // If we filled this in by default, we want to prompt the user to
+          // confirm that this is really what they want.
+          $must_prompt = true;
+        }
+      }
     }
 
-
-    return $this->newPage()
-      ->setTitle(
+    $refs = $drequest->resolveRefs(
+      array_filter(
         array(
-          $repository->getName(),
-          $repository->getDisplayName(),
-        ))
-      ->setCrumbs($crumbs)
-      ->appendChild($content);
-  }
-
-  private function buildCompareForm(AphrontRequest $request, array $resolved) {
-    $viewer = $this->getViewer();
-
-    $head_ref = $request->getStr('head');
-    $against_ref = $request->getStr('against');
+          $head_ref,
+          $against_ref,
+        )));
 
-    if (idx($resolved, $head_ref)) {
-      $e_head = null;
+    $identical = false;
+    if ($head_ref === $against_ref) {
+      $identical = true;
     } else {
-      $e_head = 'Not Found';
+      if (count($refs) == 2) {
+        if ($refs[$head_ref] === $refs[$against_ref]) {
+          $identical = true;
+        }
+      }
     }
 
-    if (idx($resolved, $against_ref)) {
-      $e_against = null;
-    } else {
-      $e_against = 'Not Found';
+    if ($must_prompt || count($refs) != 2 || $identical) {
+      return $this->buildCompareDialog(
+        $head_ref,
+        $against_ref,
+        $refs,
+        $identical);
     }
 
+    if ($request->isFormPost()) {
+      // Redirect to a stable URI that can be copy/pasted.
+      $compare_uri = $drequest->generateURI(
+        array(
+          'action' => 'compare',
+          'head' => $head_ref,
+          'against' => $against_ref,
+        ));
 
-    $form = id(new AphrontFormView())
-      ->setUser($viewer)
-      ->setMethod('GET')
-      ->appendControl(
-        id(new AphrontFormTextControl())
-          ->setLabel(pht('Head'))
-          ->setName('head')
-          ->setError($e_head)
-          ->setValue($head_ref))
-      ->appendControl(
-        id(new AphrontFormTextControl())
-          ->setLabel(pht('Against'))
-          ->setName('against')
-          ->setError($e_against)
-          ->setValue($against_ref))
-      ->appendControl(
-        id(new AphrontFormSubmitControl())
-          ->setValue('Compare'));
-
-    return $form;
-  }
-
-  private function buildCompareContent(DiffusionRequest $drequest) {
-    $request = $this->getRequest();
-    $repository = $drequest->getRepository();
-
-    $head_ref = $request->getStr('head');
-    $against_ref = $request->getStr('against');
+      return id(new AphrontRedirectResponse())->setURI($compare_uri);
+    }
 
-    $content = array();
+    $crumbs = $this->buildCrumbs(
+      array(
+        'view' => 'compare',
+      ));
 
     $pager = id(new PHUIPagerView())
       ->readFromRequest($request);
 
+    $history = null;
     try {
       $history_results = $this->callConduitWithDiffusionRequest(
         'diffusion.historyquery',
         array(
           'commit' => $head_ref,
           'against' => $against_ref,
           'path' => $drequest->getPath(),
           'offset' => $pager->getOffset(),
           'limit' => $pager->getPageSize() + 1,
         ));
       $history = DiffusionPathChange::newFromConduit(
         $history_results['pathChanges']);
-
       $history = $pager->sliceResults($history);
 
-      $history_exception = null;
+      $history_view = $this->newHistoryView(
+        $history_results,
+        $history,
+        $pager,
+        $head_ref,
+        $against_ref);
+
     } catch (Exception $ex) {
-      $history_results = null;
-      $history = null;
-      $history_exception = $ex;
+      if ($repository->isImporting()) {
+        $history_view = $this->renderStatusMessage(
+          pht('Still Importing...'),
+          pht(
+            'This repository is still importing. History is not yet '.
+            'available.'));
+      } else {
+        $history_view = $this->renderStatusMessage(
+          pht('Unable to Retrieve History'),
+          $ex->getMessage());
+      }
     }
 
-    if ($history_results) {
-        $content[] = $this->buildCompareProperties($drequest, $history_results);
-    }
-    $content[] = $this->buildCompareForm(
-      $request,
-      array($head_ref => true, $against_ref => true));
+    $header = id(new PHUIHeaderView())
+      ->setHeader(
+        pht(
+          'Changes on %s but not %s',
+          phutil_tag('em', array(), $head_ref),
+          phutil_tag('em', array(), $against_ref)));
 
-    $content[] = $this->buildHistoryTable(
-      $history_results,
-      $history,
-      $pager,
-      $history_exception);
+    $curtain = $this->buildCurtain($head_ref, $against_ref);
 
-    $content[] = $this->renderTablePagerBox($pager);
+    $column_view = id(new PHUITwoColumnView())
+      ->setHeader($header)
+      ->setCurtain($curtain)
+      ->setMainColumn(
+        array(
+          $history_view,
+        ));
 
-    return $content;
+    return $this->newPage()
+      ->setTitle(
+        array(
+          $repository->getName(),
+          $repository->getDisplayName(),
+        ))
+      ->setCrumbs($crumbs)
+      ->appendChild($column_view);
   }
 
-  private function buildCompareProperties($drequest, array $history_results) {
-    $viewer = $this->getViewer();
+  private function buildCompareDialog(
+    $head_ref,
+    $against_ref,
+    array $resolved,
+    $identical) {
 
+    $viewer = $this->getViewer();
     $request = $this->getRequest();
+    $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
-    $head_ref = $request->getStr('head');
-    $against_ref = $request->getStr('against');
+    $e_head = null;
+    $e_against = null;
+    $errors = array();
+    if ($request->isFormPost()) {
+      if (!strlen($head_ref)) {
+        $e_head = pht('Required');
+        $errors[] = pht(
+          'You must provide two different commits to compare.');
+      } else if (!isset($resolved[$head_ref])) {
+        $e_head = pht('Not Found');
+        $errors[] = pht(
+          'Commit "%s" is not a valid commit in this repository.',
+          $head_ref);
+      }
+
+      if (!strlen($against_ref)) {
+        $e_against = pht('Required');
+        $errors[] = pht(
+          'You must provide two different commits to compare.');
+      } else if (!isset($resolved[$against_ref])) {
+        $e_against = pht('Not Found');
+        $errors[] = pht(
+          'Commit "%s" is not a valid commit in this repository.',
+          $against_ref);
+      }
 
-    $reverse_uri = $repository->getPathURI(
-      "compare/?head=${against_ref}&against=${head_ref}");
-    $actions = id(new PhabricatorActionListView());
-    $actions->setUser($viewer);
+      if ($identical) {
+        $e_head = pht('Identical');
+        $e_against = pht('Identical');
+        $errors[] = pht(
+          'Both references identify the same commit. You can not compare a '.
+          'commit against itself.');
+      }
+    }
 
+    $form = id(new AphrontFormView())
+      ->setViewer($viewer)
+      ->appendControl(
+        id(new AphrontFormTextControl())
+          ->setLabel(pht('Head'))
+          ->setName('head')
+          ->setError($e_head)
+          ->setValue($head_ref))
+      ->appendControl(
+        id(new AphrontFormTextControl())
+          ->setLabel(pht('Against'))
+          ->setName('against')
+          ->setError($e_against)
+          ->setValue($against_ref));
+
+    $cancel_uri = $repository->generateURI(
+      array(
+        'action' => 'browse',
+      ));
+
+    return $this->newDialog()
+      ->setTitle(pht('Compare Against'))
+      ->setWidth(AphrontDialogView::WIDTH_FORM)
+      ->setErrors($errors)
+      ->appendForm($form)
+      ->addSubmitButton(pht('Compare'))
+      ->addCancelButton($cancel_uri, pht('Cancel'));
+  }
 
-    $actions->addAction(id(new PhabricatorActionView())
+  private function buildCurtain($head_ref, $against_ref) {
+    $viewer = $this->getViewer();
+    $request = $this->getRequest();
+    $drequest = $this->getDiffusionRequest();
+    $repository = $drequest->getRepository();
+
+    $curtain = $this->newCurtainView(null);
+
+    $reverse_uri = $drequest->generateURI(
+      array(
+        'action' => 'compare',
+        'head' => $against_ref,
+        'against' => $head_ref,
+      ));
+
+    $curtain->addAction(
+      id(new PhabricatorActionView())
         ->setName(pht('Reverse Comparison'))
         ->setHref($reverse_uri)
-        ->setIcon('fa-list'));
+        ->setIcon('fa-refresh'));
 
-    $view = id(new PHUIPropertyListView())
-      ->setUser($viewer)
-      ->setActionList($actions);
+    $compare_uri = $drequest->generateURI(
+      array(
+        'action' => 'compare',
+        'head' => $head_ref,
+      ));
 
-    $readme =
-      'These are the commits that are reachable from **Head** commit and not '.
-      'from the **Against** commit.';
-    $readme = new PHUIRemarkupView($viewer, $readme);
-    $view->addTextContent($readme);
+    $curtain->addAction(
+      id(new PhabricatorActionView())
+        ->setName(pht('Compare Against...'))
+        ->setIcon('fa-code-fork')
+        ->setWorkflow(true)
+        ->setHref($compare_uri));
 
-    $view->addProperty(pht('Head'), $head_ref);
-    $view->addProperty(pht('Against'), $against_ref);
+    // TODO: Provide a "Show Diff" action.
 
-    $header = id(new PHUIHeaderView())
-      ->setUser($viewer)
-      ->setPolicyObject($drequest->getRepository());
-
-    $box = id(new PHUIObjectBoxView())
-      ->setUser($viewer)
-      ->setHeader($header)
-      ->addPropertyList($view);
-    return $box;
+    return $curtain;
   }
 
-  private function buildHistoryTable(
-    $history_results,
-    $history,
-    $pager,
-    $history_exception) {
+  private function newHistoryView(
+    array $results,
+    array $history,
+    PHUIPagerView $pager,
+    $head_ref,
+    $against_ref) {
 
     $request = $this->getRequest();
-    $viewer = $request->getUser();
+    $viewer = $this->getViewer();
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
-    if ($history_exception) {
-      if ($repository->isImporting()) {
-        return $this->renderStatusMessage(
-          pht('Still Importing...'),
-          pht(
-            'This repository is still importing. History is not yet '.
-            'available.'));
-      } else {
-        return $this->renderStatusMessage(
-          pht('Unable to Retrieve History'),
-          $history_exception->getMessage());
-      }
-    }
-
     if (!$history) {
       return $this->renderStatusMessage(
-        pht('Up to date'),
-        new PHUIRemarkupView(
-          $viewer,
-          pht(
-            '**Against** is strictly ahead of **Head** '.
-            '- no commits are missing.')));
+        pht('Up To Date'),
+        pht(
+          'There are no commits on %s that are not already on %s.',
+          phutil_tag('strong', array(), $head_ref),
+          phutil_tag('strong', array(), $against_ref)));
     }
 
     $history_table = id(new DiffusionHistoryTableView())
       ->setUser($viewer)
       ->setDiffusionRequest($drequest)
       ->setHistory($history);
 
-    // TODO: Super sketchy?
     $history_table->loadRevisions();
 
-    if ($history_results) {
-      $history_table->setParents($history_results['parents']);
+    if ($history) {
+      $history_table->setParents($results['parents']);
       $history_table->setIsHead(!$pager->getOffset());
       $history_table->setIsTail(!$pager->getHasMorePages());
     }
 
-    // TODO also expose diff.
-
-    $panel = new PHUIObjectBoxView();
     $header = id(new PHUIHeaderView())
-      ->setHeader(pht('Missing Commits'));
-    $panel->setHeader($header);
-    $panel->setTable($history_table);
+      ->setHeader(pht('Commits'));
+
+    $object_box = id(new PHUIObjectBoxView())
+      ->setHeader($header)
+      ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
+      ->setTable($history_table);
+
+    $pager_box = $this->renderTablePagerBox($pager);
 
-    return $panel;
+    return array(
+      $object_box,
+      $pager_box,
+    );
   }
 }
diff --git a/src/applications/diffusion/request/DiffusionRequest.php b/src/applications/diffusion/request/DiffusionRequest.php
index 417052b594..ab08025349 100644
--- a/src/applications/diffusion/request/DiffusionRequest.php
+++ b/src/applications/diffusion/request/DiffusionRequest.php
@@ -1,694 +1,694 @@
 <?php
 
 /**
  * Contains logic to parse Diffusion requests, which have a complicated URI
  * structure.
  *
  * @task new Creating Requests
  * @task uri Managing Diffusion URIs
  */
 abstract class DiffusionRequest extends Phobject {
 
   protected $path;
   protected $line;
   protected $branch;
   protected $lint;
 
   protected $symbolicCommit;
   protected $symbolicType;
   protected $stableCommit;
 
   protected $repository;
   protected $repositoryCommit;
   protected $repositoryCommitData;
 
   private $isClusterRequest = false;
   private $initFromConduit = true;
   private $user;
   private $branchObject = false;
   private $refAlternatives;
 
   abstract public function supportsBranches();
   abstract protected function isStableCommit($symbol);
 
   protected function didInitialize() {
     return null;
   }
 
 
 /* -(  Creating Requests  )-------------------------------------------------- */
 
 
   /**
    * Create a new synthetic request from a parameter dictionary. If you need
    * a @{class:DiffusionRequest} object in order to issue a DiffusionQuery, you
    * can use this method to build one.
    *
    * Parameters are:
    *
    *   - `repository` Repository object or identifier.
    *   - `user` Viewing user. Required if `repository` is an identifier.
    *   - `branch` Optional, branch name.
    *   - `path` Optional, file path.
    *   - `commit` Optional, commit identifier.
    *   - `line` Optional, line range.
    *
    * @param   map                 See documentation.
    * @return  DiffusionRequest    New request object.
    * @task new
    */
   final public static function newFromDictionary(array $data) {
     $repository_key = 'repository';
     $identifier_key = 'callsign';
     $viewer_key = 'user';
 
     $repository = idx($data, $repository_key);
     $identifier = idx($data, $identifier_key);
 
     $have_repository = ($repository !== null);
     $have_identifier = ($identifier !== null);
 
     if ($have_repository && $have_identifier) {
       throw new Exception(
         pht(
           'Specify "%s" or "%s", but not both.',
           $repository_key,
           $identifier_key));
     }
 
     if (!$have_repository && !$have_identifier) {
       throw new Exception(
         pht(
           'One of "%s" and "%s" is required.',
           $repository_key,
           $identifier_key));
     }
 
     if ($have_repository) {
       if (!($repository instanceof PhabricatorRepository)) {
         if (empty($data[$viewer_key])) {
           throw new Exception(
             pht(
               'Parameter "%s" is required if "%s" is provided.',
               $viewer_key,
               $identifier_key));
         }
 
         $identifier = $repository;
         $repository = null;
       }
     }
 
     if ($identifier !== null) {
       $object = self::newFromIdentifier(
         $identifier,
         $data[$viewer_key],
         idx($data, 'edit'));
     } else {
       $object = self::newFromRepository($repository);
     }
 
     if (!$object) {
       return null;
     }
 
     $object->initializeFromDictionary($data);
 
     return $object;
   }
 
   /**
    * Internal.
    *
    * @task new
    */
   final private function __construct() {
     // <private>
   }
 
 
   /**
    * Internal. Use @{method:newFromDictionary}, not this method.
    *
    * @param   string              Repository identifier.
    * @param   PhabricatorUser     Viewing user.
    * @return  DiffusionRequest    New request object.
    * @task new
    */
   final private static function newFromIdentifier(
     $identifier,
     PhabricatorUser $viewer,
     $need_edit = false) {
 
     $query = id(new PhabricatorRepositoryQuery())
       ->setViewer($viewer)
       ->withIdentifiers(array($identifier))
       ->needURIs(true);
 
     if ($need_edit) {
       $query->requireCapabilities(
         array(
           PhabricatorPolicyCapability::CAN_VIEW,
           PhabricatorPolicyCapability::CAN_EDIT,
         ));
     }
 
     $repository = $query->executeOne();
 
     if (!$repository) {
       return null;
     }
 
     return self::newFromRepository($repository);
   }
 
 
   /**
    * Internal. Use @{method:newFromDictionary}, not this method.
    *
    * @param   PhabricatorRepository   Repository object.
    * @return  DiffusionRequest        New request object.
    * @task new
    */
   final private static function newFromRepository(
     PhabricatorRepository $repository) {
 
     $map = array(
       PhabricatorRepositoryType::REPOSITORY_TYPE_GIT => 'DiffusionGitRequest',
       PhabricatorRepositoryType::REPOSITORY_TYPE_SVN => 'DiffusionSvnRequest',
       PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL =>
         'DiffusionMercurialRequest',
     );
 
     $class = idx($map, $repository->getVersionControlSystem());
 
     if (!$class) {
       throw new Exception(pht('Unknown version control system!'));
     }
 
     $object = new $class();
 
     $object->repository = $repository;
 
     return $object;
   }
 
 
   /**
    * Internal. Use @{method:newFromDictionary}, not this method.
    *
    * @param map Map of parsed data.
    * @return void
    * @task new
    */
   final private function initializeFromDictionary(array $data) {
     $blob = idx($data, 'blob');
     if (strlen($blob)) {
       $blob = self::parseRequestBlob($blob, $this->supportsBranches());
       $data = $blob + $data;
     }
 
     $this->path = idx($data, 'path');
     $this->line = idx($data, 'line');
     $this->initFromConduit = idx($data, 'initFromConduit', true);
     $this->lint = idx($data, 'lint');
 
     $this->symbolicCommit = idx($data, 'commit');
     if ($this->supportsBranches()) {
       $this->branch = idx($data, 'branch');
     }
 
     if (!$this->getUser()) {
       $user = idx($data, 'user');
       if (!$user) {
         throw new Exception(
           pht(
             'You must provide a %s in the dictionary!',
             'PhabricatorUser'));
       }
       $this->setUser($user);
     }
 
     $this->didInitialize();
   }
 
   final public function setUser(PhabricatorUser $user) {
     $this->user = $user;
     return $this;
   }
   final public function getUser() {
     return $this->user;
   }
 
   public function getRepository() {
     return $this->repository;
   }
 
   public function setPath($path) {
     $this->path = $path;
     return $this;
   }
 
   public function getPath() {
     return $this->path;
   }
 
   public function getLine() {
     return $this->line;
   }
 
   public function getCommit() {
 
     // TODO: Probably remove all of this.
 
     if ($this->getSymbolicCommit() !== null) {
       return $this->getSymbolicCommit();
     }
 
     return $this->getStableCommit();
   }
 
   /**
    * Get the symbolic commit associated with this request.
    *
    * A symbolic commit may be a commit hash, an abbreviated commit hash, a
    * branch name, a tag name, or an expression like "HEAD^^^". The symbolic
    * commit may also be absent.
    *
    * This method always returns the symbol present in the original request,
    * in unmodified form.
    *
    * See also @{method:getStableCommit}.
    *
    * @return string|null  Symbolic commit, if one was present in the request.
    */
   public function getSymbolicCommit() {
     return $this->symbolicCommit;
   }
 
 
   /**
    * Modify the request to move the symbolic commit elsewhere.
    *
    * @param string New symbolic commit.
    * @return this
    */
   public function updateSymbolicCommit($symbol) {
     $this->symbolicCommit = $symbol;
     $this->symbolicType = null;
     $this->stableCommit = null;
     return $this;
   }
 
 
   /**
    * Get the ref type (`commit` or `tag`) of the location associated with this
    * request.
    *
    * If a symbolic commit is present in the request, this method identifies
    * the type of the symbol. Otherwise, it identifies the type of symbol of
    * the location the request is implicitly associated with. This will probably
    * always be `commit`.
    *
    * @return string   Symbolic commit type (`commit` or `tag`).
    */
   public function getSymbolicType() {
     if ($this->symbolicType === null) {
       // As a side effect, this resolves the symbolic type.
       $this->getStableCommit();
     }
     return $this->symbolicType;
   }
 
 
   /**
    * Retrieve the stable, permanent commit name identifying the repository
    * location associated with this request.
    *
    * This returns a non-symbolic identifier for the current commit: in Git and
    * Mercurial, a 40-character SHA1; in SVN, a revision number.
    *
    * See also @{method:getSymbolicCommit}.
    *
    * @return string Stable commit name, like a git hash or SVN revision. Not
    *                a symbolic commit reference.
    */
   public function getStableCommit() {
     if (!$this->stableCommit) {
       if ($this->isStableCommit($this->symbolicCommit)) {
         $this->stableCommit = $this->symbolicCommit;
         $this->symbolicType = 'commit';
       } else {
         $this->queryStableCommit();
       }
     }
     return $this->stableCommit;
   }
 
 
   public function getBranch() {
     return $this->branch;
   }
 
   public function getLint() {
     return $this->lint;
   }
 
   protected function getArcanistBranch() {
     return $this->getBranch();
   }
 
   public function loadBranch() {
     // TODO: Get rid of this and do real Queries on real objects.
 
     if ($this->branchObject === false) {
       $this->branchObject = PhabricatorRepositoryBranch::loadBranch(
         $this->getRepository()->getID(),
         $this->getArcanistBranch());
     }
 
     return $this->branchObject;
   }
 
   public function loadCoverage() {
     // TODO: This should also die.
     $branch = $this->loadBranch();
     if (!$branch) {
       return;
     }
 
     $path = $this->getPath();
     $path_map = id(new DiffusionPathIDQuery(array($path)))->loadPathIDs();
 
     $coverage_row = queryfx_one(
       id(new PhabricatorRepository())->establishConnection('r'),
       'SELECT * FROM %T WHERE branchID = %d AND pathID = %d
         ORDER BY commitID DESC LIMIT 1',
       'repository_coverage',
       $branch->getID(),
       $path_map[$path]);
 
     if (!$coverage_row) {
       return null;
     }
 
     return idx($coverage_row, 'coverage');
   }
 
 
   public function loadCommit() {
     if (empty($this->repositoryCommit)) {
       $repository = $this->getRepository();
 
       $commit = id(new DiffusionCommitQuery())
         ->setViewer($this->getUser())
         ->withRepository($repository)
         ->withIdentifiers(array($this->getStableCommit()))
         ->executeOne();
       if ($commit) {
         $commit->attachRepository($repository);
       }
       $this->repositoryCommit = $commit;
     }
     return $this->repositoryCommit;
   }
 
   public function loadCommitData() {
     if (empty($this->repositoryCommitData)) {
       $commit = $this->loadCommit();
       $data = id(new PhabricatorRepositoryCommitData())->loadOneWhere(
         'commitID = %d',
         $commit->getID());
       if (!$data) {
         $data = new PhabricatorRepositoryCommitData();
         $data->setCommitMessage(
           pht('(This commit has not been fully parsed yet.)'));
       }
       $this->repositoryCommitData = $data;
     }
     return $this->repositoryCommitData;
   }
 
 /* -(  Managing Diffusion URIs  )-------------------------------------------- */
 
 
   public function generateURI(array $params) {
     if (empty($params['stable'])) {
       $default_commit = $this->getSymbolicCommit();
     } else {
       $default_commit = $this->getStableCommit();
     }
 
     $defaults = array(
       'path'      => $this->getPath(),
       'branch'    => $this->getBranch(),
       'commit'    => $default_commit,
       'lint'      => idx($params, 'lint', $this->getLint()),
     );
 
     foreach ($defaults as $key => $val) {
       if (!isset($params[$key])) { // Overwrite NULL.
         $params[$key] = $val;
       }
     }
 
     return $this->getRepository()->generateURI($params);
   }
 
   /**
    * Internal. Public only for unit tests.
    *
    * Parse the request URI into components.
    *
    * @param   string  URI blob.
    * @param   bool    True if this VCS supports branches.
    * @return  map     Parsed URI.
    *
    * @task uri
    */
   public static function parseRequestBlob($blob, $supports_branches) {
     $result = array(
       'branch'  => null,
       'path'    => null,
       'commit'  => null,
       'line'    => null,
     );
 
     $matches = null;
 
     if ($supports_branches) {
       // Consume the front part of the URI, up to the first "/". This is the
       // path-component encoded branch name.
       if (preg_match('@^([^/]+)/@', $blob, $matches)) {
         $result['branch'] = phutil_unescape_uri_path_component($matches[1]);
         $blob = substr($blob, strlen($matches[1]) + 1);
       }
     }
 
     // Consume the back part of the URI, up to the first "$". Use a negative
     // lookbehind to prevent matching '$$'. We double the '$' symbol when
     // encoding so that files with names like "money/$100" will survive.
     $pattern = '@(?:(?:^|[^$])(?:[$][$])*)[$]([\d-,]+)$@';
     if (preg_match($pattern, $blob, $matches)) {
       $result['line'] = $matches[1];
       $blob = substr($blob, 0, -(strlen($matches[1]) + 1));
     }
 
     // We've consumed the line number if it exists, so unescape "$" in the
     // rest of the string.
     $blob = str_replace('$$', '$', $blob);
 
     // Consume the commit name, stopping on ';;'. We allow any character to
     // appear in commits names, as they can sometimes be symbolic names (like
     // tag names or refs).
     if (preg_match('@(?:(?:^|[^;])(?:;;)*);([^;].*)$@', $blob, $matches)) {
       $result['commit'] = $matches[1];
       $blob = substr($blob, 0, -(strlen($matches[1]) + 1));
     }
 
     // We've consumed the commit if it exists, so unescape ";" in the rest
     // of the string.
     $blob = str_replace(';;', ';', $blob);
 
     if (strlen($blob)) {
       $result['path'] = $blob;
     }
 
     $parts = explode('/', $result['path']);
     foreach ($parts as $part) {
       // Prevent any hyjinx since we're ultimately shipping this to the
       // filesystem under a lot of workflows.
       if ($part == '..') {
         throw new Exception(pht('Invalid path URI.'));
       }
     }
 
     return $result;
   }
 
   /**
    * Check that the working copy of the repository is present and readable.
    *
    * @param   string  Path to the working copy.
    */
   protected function validateWorkingCopy($path) {
     if (!is_readable(dirname($path))) {
       $this->raisePermissionException();
     }
 
     if (!Filesystem::pathExists($path)) {
       $this->raiseCloneException();
     }
   }
 
   protected function raisePermissionException() {
     $host = php_uname('n');
     throw new DiffusionSetupException(
       pht(
         'The clone of this repository ("%s") on the local machine ("%s") '.
         'could not be read. Ensure that the repository is in a '.
         'location where the web server has read permissions.',
         $this->getRepository()->getDisplayName(),
         $host));
   }
 
   protected function raiseCloneException() {
     $host = php_uname('n');
     throw new DiffusionSetupException(
       pht(
         'The working copy for this repository ("%s") has not been cloned yet '.
         'on this machine ("%s"). Make sure you havestarted the Phabricator '.
         'daemons. If this problem persists for longer than a clone should '.
         'take, check the daemon logs (in the Daemon Console) to see if there '.
         'were errors cloning the repository. Consult the "Diffusion User '.
         'Guide" in the documentation for help setting up repositories.',
         $this->getRepository()->getDisplayName(),
         $host));
   }
 
   private function queryStableCommit() {
     $types = array();
     if ($this->symbolicCommit) {
       $ref = $this->symbolicCommit;
     } else {
       if ($this->supportsBranches()) {
         $ref = $this->getBranch();
         $types = array(
           PhabricatorRepositoryRefCursor::TYPE_BRANCH,
         );
       } else {
         $ref = 'HEAD';
       }
     }
 
     $results = $this->resolveRefs(array($ref), $types);
 
     $matches = idx($results, $ref, array());
     if (!$matches) {
       $message = pht(
         'Ref "%s" does not exist in this repository.',
         $ref);
       throw id(new DiffusionRefNotFoundException($message))
         ->setRef($ref);
     }
 
     if (count($matches) > 1) {
       $match = $this->chooseBestRefMatch($ref, $matches);
     } else {
       $match = head($matches);
     }
 
     $this->stableCommit = $match['identifier'];
     $this->symbolicType = $match['type'];
   }
 
   public function getRefAlternatives() {
     // Make sure we've resolved the reference into a stable commit first.
     try {
       $this->getStableCommit();
     } catch (DiffusionRefNotFoundException $ex) {
       // If we have a bad reference, just return the empty set of
       // alternatives.
     }
     return $this->refAlternatives;
   }
 
   private function chooseBestRefMatch($ref, array $results) {
     // First, filter out less-desirable matches.
     $candidates = array();
     foreach ($results as $result) {
       // Exclude closed heads.
       if ($result['type'] == 'branch') {
         if (idx($result, 'closed')) {
           continue;
         }
       }
 
       $candidates[] = $result;
     }
 
     // If we filtered everything, undo the filtering.
     if (!$candidates) {
       $candidates = $results;
     }
 
     // TODO: Do a better job of selecting the best match?
     $match = head($candidates);
 
     // After choosing the best alternative, save all the alternatives so the
     // UI can show them to the user.
     if (count($candidates) > 1) {
       $this->refAlternatives = $candidates;
     }
 
     return $match;
   }
 
-  private function resolveRefs(array $refs, array $types) {
+  public function resolveRefs(array $refs, array $types = array()) {
     // First, try to resolve refs from fast cache sources.
     $cached_query = id(new DiffusionCachedResolveRefsQuery())
       ->setRepository($this->getRepository())
       ->withRefs($refs);
 
     if ($types) {
       $cached_query->withTypes($types);
     }
 
     $cached_results = $cached_query->execute();
 
     // Throw away all the refs we resolved. Hopefully, we'll throw away
     // everything here.
     foreach ($refs as $key => $ref) {
       if (isset($cached_results[$ref])) {
         unset($refs[$key]);
       }
     }
 
     // If we couldn't pull everything out of the cache, execute the underlying
     // VCS operation.
     if ($refs) {
       $vcs_results = DiffusionQuery::callConduitWithDiffusionRequest(
         $this->getUser(),
         $this,
         'diffusion.resolverefs',
         array(
           'types' => $types,
           'refs' => $refs,
         ));
     } else {
       $vcs_results = array();
     }
 
     return $vcs_results + $cached_results;
   }
 
   public function setIsClusterRequest($is_cluster_request) {
     $this->isClusterRequest = $is_cluster_request;
     return $this;
   }
 
   public function getIsClusterRequest() {
     return $this->isClusterRequest;
   }
 
 }
diff --git a/src/applications/repository/storage/PhabricatorRepository.php b/src/applications/repository/storage/PhabricatorRepository.php
index 17415fb496..cc1942d8d2 100644
--- a/src/applications/repository/storage/PhabricatorRepository.php
+++ b/src/applications/repository/storage/PhabricatorRepository.php
@@ -1,2510 +1,2537 @@
 <?php
 
 /**
  * @task uri        Repository URI Management
  * @task autoclose  Autoclose
  * @task sync       Cluster Synchronization
  */
 final class PhabricatorRepository extends PhabricatorRepositoryDAO
   implements
     PhabricatorApplicationTransactionInterface,
     PhabricatorPolicyInterface,
     PhabricatorFlaggableInterface,
     PhabricatorMarkupInterface,
     PhabricatorDestructibleInterface,
     PhabricatorProjectInterface,
     PhabricatorSpacesInterface,
     PhabricatorConduitResultInterface {
 
   /**
    * Shortest hash we'll recognize in raw "a829f32" form.
    */
   const MINIMUM_UNQUALIFIED_HASH = 7;
 
   /**
    * Shortest hash we'll recognize in qualified "rXab7ef2f8" form.
    */
   const MINIMUM_QUALIFIED_HASH = 5;
 
   /**
    * Minimum number of commits to an empty repository to trigger "import" mode.
    */
   const IMPORT_THRESHOLD = 7;
 
   const TABLE_PATH = 'repository_path';
   const TABLE_PATHCHANGE = 'repository_pathchange';
   const TABLE_FILESYSTEM = 'repository_filesystem';
   const TABLE_SUMMARY = 'repository_summary';
   const TABLE_LINTMESSAGE = 'repository_lintmessage';
   const TABLE_PARENTS = 'repository_parents';
   const TABLE_COVERAGE = 'repository_coverage';
 
   const BECAUSE_REPOSITORY_IMPORTING = 'auto/importing';
   const BECAUSE_AUTOCLOSE_DISABLED = 'auto/disabled';
   const BECAUSE_NOT_ON_AUTOCLOSE_BRANCH = 'auto/nobranch';
   const BECAUSE_BRANCH_UNTRACKED = 'auto/notrack';
   const BECAUSE_BRANCH_NOT_AUTOCLOSE = 'auto/noclose';
   const BECAUSE_AUTOCLOSE_FORCED = 'auto/forced';
 
   const STATUS_ACTIVE = 'active';
   const STATUS_INACTIVE = 'inactive';
 
   protected $name;
   protected $callsign;
   protected $repositorySlug;
   protected $uuid;
   protected $viewPolicy;
   protected $editPolicy;
   protected $pushPolicy;
 
   protected $versionControlSystem;
   protected $details = array();
   protected $credentialPHID;
   protected $almanacServicePHID;
   protected $spacePHID;
   protected $localPath;
 
   private $commitCount = self::ATTACHABLE;
   private $mostRecentCommit = self::ATTACHABLE;
   private $projectPHIDs = self::ATTACHABLE;
   private $uris = self::ATTACHABLE;
 
 
   public static function initializeNewRepository(PhabricatorUser $actor) {
     $app = id(new PhabricatorApplicationQuery())
       ->setViewer($actor)
       ->withClasses(array('PhabricatorDiffusionApplication'))
       ->executeOne();
 
     $view_policy = $app->getPolicy(DiffusionDefaultViewCapability::CAPABILITY);
     $edit_policy = $app->getPolicy(DiffusionDefaultEditCapability::CAPABILITY);
     $push_policy = $app->getPolicy(DiffusionDefaultPushCapability::CAPABILITY);
 
     $repository = id(new PhabricatorRepository())
       ->setViewPolicy($view_policy)
       ->setEditPolicy($edit_policy)
       ->setPushPolicy($push_policy)
       ->setSpacePHID($actor->getDefaultSpacePHID());
 
     // Put the repository in "Importing" mode until we finish
     // parsing it.
     $repository->setDetail('importing', true);
 
     return $repository;
   }
 
   protected function getConfiguration() {
     return array(
       self::CONFIG_AUX_PHID => true,
       self::CONFIG_SERIALIZATION => array(
         'details' => self::SERIALIZATION_JSON,
       ),
       self::CONFIG_COLUMN_SCHEMA => array(
         'name' => 'sort255',
         'callsign' => 'sort32?',
         'repositorySlug' => 'sort64?',
         'versionControlSystem' => 'text32',
         'uuid' => 'text64?',
         'pushPolicy' => 'policy',
         'credentialPHID' => 'phid?',
         'almanacServicePHID' => 'phid?',
         'localPath' => 'text128?',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'callsign' => array(
           'columns' => array('callsign'),
           'unique' => true,
         ),
         'key_name' => array(
           'columns' => array('name(128)'),
         ),
         'key_vcs' => array(
           'columns' => array('versionControlSystem'),
         ),
         'key_slug' => array(
           'columns' => array('repositorySlug'),
           'unique' => true,
         ),
         'key_local' => array(
           'columns' => array('localPath'),
           'unique' => true,
         ),
       ),
     ) + parent::getConfiguration();
   }
 
   public function generatePHID() {
     return PhabricatorPHID::generateNewPHID(
       PhabricatorRepositoryRepositoryPHIDType::TYPECONST);
   }
 
   public static function getStatusMap() {
     return array(
       self::STATUS_ACTIVE => array(
         'name' => pht('Active'),
         'isTracked' => 1,
       ),
       self::STATUS_INACTIVE => array(
         'name' => pht('Inactive'),
         'isTracked' => 0,
       ),
     );
   }
 
   public static function getStatusNameMap() {
     return ipull(self::getStatusMap(), 'name');
   }
 
   public function getStatus() {
     if ($this->isTracked()) {
       return self::STATUS_ACTIVE;
     } else {
       return self::STATUS_INACTIVE;
     }
   }
 
   public function toDictionary() {
     return array(
       'id'          => $this->getID(),
       'name'        => $this->getName(),
       'phid'        => $this->getPHID(),
       'callsign'    => $this->getCallsign(),
       'monogram'    => $this->getMonogram(),
       'vcs'         => $this->getVersionControlSystem(),
       'uri'         => PhabricatorEnv::getProductionURI($this->getURI()),
       'remoteURI'   => (string)$this->getRemoteURI(),
       'description' => $this->getDetail('description'),
       'isActive'    => $this->isTracked(),
       'isHosted'    => $this->isHosted(),
       'isImporting' => $this->isImporting(),
       'encoding'    => $this->getDefaultTextEncoding(),
       'staging' => array(
         'supported' => $this->supportsStaging(),
         'prefix' => 'phabricator',
         'uri' => $this->getStagingURI(),
       ),
     );
   }
 
   public function getDefaultTextEncoding() {
     return $this->getDetail('encoding', 'UTF-8');
   }
 
   public function getMonogram() {
     $callsign = $this->getCallsign();
     if (strlen($callsign)) {
       return "r{$callsign}";
     }
 
     $id = $this->getID();
     return "R{$id}";
   }
 
   public function getDisplayName() {
     $slug = $this->getRepositorySlug();
     if (strlen($slug)) {
       return $slug;
     }
 
     return $this->getMonogram();
   }
 
   public function getAllMonograms() {
     $monograms = array();
 
     $monograms[] = 'R'.$this->getID();
 
     $callsign = $this->getCallsign();
     if (strlen($callsign)) {
       $monograms[] = 'r'.$callsign;
     }
 
     return $monograms;
   }
 
   public function setLocalPath($path) {
     // Convert any extra slashes ("//") in the path to a single slash ("/").
     $path = preg_replace('(//+)', '/', $path);
 
     return parent::setLocalPath($path);
   }
 
   public function getDetail($key, $default = null) {
     return idx($this->details, $key, $default);
   }
 
   public function getHumanReadableDetail($key, $default = null) {
     $value = $this->getDetail($key, $default);
 
     switch ($key) {
       case 'branch-filter':
       case 'close-commits-filter':
         $value = array_keys($value);
         $value = implode(', ', $value);
         break;
     }
 
     return $value;
   }
 
   public function setDetail($key, $value) {
     $this->details[$key] = $value;
     return $this;
   }
 
   public function attachCommitCount($count) {
     $this->commitCount = $count;
     return $this;
   }
 
   public function getCommitCount() {
     return $this->assertAttached($this->commitCount);
   }
 
   public function attachMostRecentCommit(
     PhabricatorRepositoryCommit $commit = null) {
     $this->mostRecentCommit = $commit;
     return $this;
   }
 
   public function getMostRecentCommit() {
     return $this->assertAttached($this->mostRecentCommit);
   }
 
   public function getDiffusionBrowseURIForPath(
     PhabricatorUser $user,
     $path,
     $line = null,
     $branch = null) {
 
     $drequest = DiffusionRequest::newFromDictionary(
       array(
         'user' => $user,
         'repository' => $this,
         'path' => $path,
         'branch' => $branch,
       ));
 
     return $drequest->generateURI(
       array(
         'action' => 'browse',
         'line'   => $line,
       ));
   }
 
   public function getSubversionBaseURI($commit = null) {
     $subpath = $this->getDetail('svn-subpath');
     if (!strlen($subpath)) {
       $subpath = null;
     }
     return $this->getSubversionPathURI($subpath, $commit);
   }
 
   public function getSubversionPathURI($path = null, $commit = null) {
     $vcs = $this->getVersionControlSystem();
     if ($vcs != PhabricatorRepositoryType::REPOSITORY_TYPE_SVN) {
       throw new Exception(pht('Not a subversion repository!'));
     }
 
     if ($this->isHosted()) {
       $uri = 'file://'.$this->getLocalPath();
     } else {
       $uri = $this->getDetail('remote-uri');
     }
 
     $uri = rtrim($uri, '/');
 
     if (strlen($path)) {
       $path = rawurlencode($path);
       $path = str_replace('%2F', '/', $path);
       $uri = $uri.'/'.ltrim($path, '/');
     }
 
     if ($path !== null || $commit !== null) {
       $uri .= '@';
     }
 
     if ($commit !== null) {
       $uri .= $commit;
     }
 
     return $uri;
   }
 
   public function attachProjectPHIDs(array $project_phids) {
     $this->projectPHIDs = $project_phids;
     return $this;
   }
 
   public function getProjectPHIDs() {
     return $this->assertAttached($this->projectPHIDs);
   }
 
 
   /**
    * Get the name of the directory this repository should clone or checkout
    * into. For example, if the repository name is "Example Repository", a
    * reasonable name might be "example-repository". This is used to help users
    * get reasonable results when cloning repositories, since they generally do
    * not want to clone into directories called "X/" or "Example Repository/".
    *
    * @return string
    */
   public function getCloneName() {
     $name = $this->getRepositorySlug();
 
     // Make some reasonable effort to produce reasonable default directory
     // names from repository names.
     if (!strlen($name)) {
       $name = $this->getName();
       $name = phutil_utf8_strtolower($name);
       $name = preg_replace('@[/ -:<>]+@', '-', $name);
       $name = trim($name, '-');
       if (!strlen($name)) {
         $name = $this->getCallsign();
       }
     }
 
     return $name;
   }
 
   public static function isValidRepositorySlug($slug) {
     try {
       self::assertValidRepositorySlug($slug);
       return true;
     } catch (Exception $ex) {
       return false;
     }
   }
 
   public static function assertValidRepositorySlug($slug) {
     if (!strlen($slug)) {
       throw new Exception(
         pht(
           'The empty string is not a valid repository short name. '.
           'Repository short names must be at least one character long.'));
     }
 
     if (strlen($slug) > 64) {
       throw new Exception(
         pht(
           'The name "%s" is not a valid repository short name. Repository '.
           'short names must not be longer than 64 characters.',
           $slug));
     }
 
     if (preg_match('/[^a-zA-Z0-9._-]/', $slug)) {
       throw new Exception(
         pht(
           'The name "%s" is not a valid repository short name. Repository '.
           'short names may only contain letters, numbers, periods, hyphens '.
           'and underscores.',
           $slug));
     }
 
     if (!preg_match('/^[a-zA-Z0-9]/', $slug)) {
       throw new Exception(
         pht(
           'The name "%s" is not a valid repository short name. Repository '.
           'short names must begin with a letter or number.',
           $slug));
     }
 
     if (!preg_match('/[a-zA-Z0-9]\z/', $slug)) {
       throw new Exception(
         pht(
           'The name "%s" is not a valid repository short name. Repository '.
           'short names must end with a letter or number.',
           $slug));
     }
 
     if (preg_match('/__|--|\\.\\./', $slug)) {
       throw new Exception(
         pht(
           'The name "%s" is not a valid repository short name. Repository '.
           'short names must not contain multiple consecutive underscores, '.
           'hyphens, or periods.',
           $slug));
     }
 
     if (preg_match('/^[A-Z]+\z/', $slug)) {
       throw new Exception(
         pht(
           'The name "%s" is not a valid repository short name. Repository '.
           'short names may not contain only uppercase letters.',
           $slug));
     }
 
     if (preg_match('/^\d+\z/', $slug)) {
       throw new Exception(
         pht(
           'The name "%s" is not a valid repository short name. Repository '.
           'short names may not contain only numbers.',
           $slug));
     }
 
     if (preg_match('/\\.git/', $slug)) {
       throw new Exception(
         pht(
           'The name "%s" is not a valid repository short name. Repository '.
           'short names must not end in ".git". This suffix will be added '.
           'automatically in appropriate contexts.',
           $slug));
     }
   }
 
   public static function assertValidCallsign($callsign) {
     if (!strlen($callsign)) {
       throw new Exception(
         pht(
           'A repository callsign must be at least one character long.'));
     }
 
     if (strlen($callsign) > 32) {
       throw new Exception(
         pht(
           'The callsign "%s" is not a valid repository callsign. Callsigns '.
           'must be no more than 32 bytes long.',
           $callsign));
     }
 
     if (!preg_match('/^[A-Z]+\z/', $callsign)) {
       throw new Exception(
         pht(
           'The callsign "%s" is not a valid repository callsign. Callsigns '.
           'may only contain UPPERCASE letters.',
           $callsign));
     }
   }
 
 
 /* -(  Remote Command Execution  )------------------------------------------- */
 
 
   public function execRemoteCommand($pattern /* , $arg, ... */) {
     $args = func_get_args();
     return $this->newRemoteCommandFuture($args)->resolve();
   }
 
   public function execxRemoteCommand($pattern /* , $arg, ... */) {
     $args = func_get_args();
     return $this->newRemoteCommandFuture($args)->resolvex();
   }
 
   public function getRemoteCommandFuture($pattern /* , $arg, ... */) {
     $args = func_get_args();
     return $this->newRemoteCommandFuture($args);
   }
 
   public function passthruRemoteCommand($pattern /* , $arg, ... */) {
     $args = func_get_args();
     return $this->newRemoteCommandPassthru($args)->execute();
   }
 
   private function newRemoteCommandFuture(array $argv) {
     return $this->newRemoteCommandEngine($argv)
       ->newFuture();
   }
 
   private function newRemoteCommandPassthru(array $argv) {
     return $this->newRemoteCommandEngine($argv)
       ->setPassthru(true)
       ->newFuture();
   }
 
   private function newRemoteCommandEngine(array $argv) {
     return DiffusionCommandEngine::newCommandEngine($this)
       ->setArgv($argv)
       ->setCredentialPHID($this->getCredentialPHID())
       ->setURI($this->getRemoteURIObject());
   }
 
 /* -(  Local Command Execution  )-------------------------------------------- */
 
 
   public function execLocalCommand($pattern /* , $arg, ... */) {
     $args = func_get_args();
     return $this->newLocalCommandFuture($args)->resolve();
   }
 
   public function execxLocalCommand($pattern /* , $arg, ... */) {
     $args = func_get_args();
     return $this->newLocalCommandFuture($args)->resolvex();
   }
 
   public function getLocalCommandFuture($pattern /* , $arg, ... */) {
     $args = func_get_args();
     return $this->newLocalCommandFuture($args);
   }
 
   public function passthruLocalCommand($pattern /* , $arg, ... */) {
     $args = func_get_args();
     return $this->newLocalCommandPassthru($args)->execute();
   }
 
   private function newLocalCommandFuture(array $argv) {
     $this->assertLocalExists();
 
     $future = DiffusionCommandEngine::newCommandEngine($this)
       ->setArgv($argv)
       ->newFuture();
 
     if ($this->usesLocalWorkingCopy()) {
       $future->setCWD($this->getLocalPath());
     }
 
     return $future;
   }
 
   private function newLocalCommandPassthru(array $argv) {
     $this->assertLocalExists();
 
     $future = DiffusionCommandEngine::newCommandEngine($this)
       ->setArgv($argv)
       ->setPassthru(true)
       ->newFuture();
 
     if ($this->usesLocalWorkingCopy()) {
       $future->setCWD($this->getLocalPath());
     }
 
     return $future;
   }
 
   public function getURI() {
     $short_name = $this->getRepositorySlug();
     if (strlen($short_name)) {
       return "/source/{$short_name}/";
     }
 
     $callsign = $this->getCallsign();
     if (strlen($callsign)) {
       return "/diffusion/{$callsign}/";
     }
 
     $id = $this->getID();
     return "/diffusion/{$id}/";
   }
 
   public function getPathURI($path) {
     return $this->getURI().ltrim($path, '/');
   }
 
   public function getCommitURI($identifier) {
     $callsign = $this->getCallsign();
     if (strlen($callsign)) {
       return "/r{$callsign}{$identifier}";
     }
 
     $id = $this->getID();
     return "/R{$id}:{$identifier}";
   }
 
   public static function parseRepositoryServicePath($request_path, $vcs) {
     $is_git = ($vcs == PhabricatorRepositoryType::REPOSITORY_TYPE_GIT);
 
     $patterns = array(
       '(^'.
         '(?P<base>/?(?:diffusion|source)/(?P<identifier>[^/]+))'.
         '(?P<path>.*)'.
       '\z)',
     );
 
     $identifier = null;
     foreach ($patterns as $pattern) {
       $matches = null;
       if (!preg_match($pattern, $request_path, $matches)) {
         continue;
       }
 
       $identifier = $matches['identifier'];
       if ($is_git) {
         $identifier = preg_replace('/\\.git\z/', '', $identifier);
       }
 
       $base = $matches['base'];
       $path = $matches['path'];
       break;
     }
 
     if ($identifier === null) {
       return null;
     }
 
     return array(
       'identifier' => $identifier,
       'base' => $base,
       'path' => $path,
     );
   }
 
   public function getCanonicalPath($request_path) {
     $standard_pattern =
       '(^'.
         '(?P<prefix>/(?:diffusion|source)/)'.
         '(?P<identifier>[^/]+)'.
         '(?P<suffix>(?:/.*)?)'.
       '\z)';
 
     $matches = null;
     if (preg_match($standard_pattern, $request_path, $matches)) {
       $suffix = $matches['suffix'];
       return $this->getPathURI($suffix);
     }
 
     $commit_pattern =
       '(^'.
         '(?P<prefix>/)'.
         '(?P<monogram>'.
           '(?:'.
             'r(?P<repositoryCallsign>[A-Z]+)'.
             '|'.
             'R(?P<repositoryID>[1-9]\d*):'.
           ')'.
           '(?P<commit>[a-f0-9]+)'.
         ')'.
       '\z)';
 
     $matches = null;
     if (preg_match($commit_pattern, $request_path, $matches)) {
       $commit = $matches['commit'];
       return $this->getCommitURI($commit);
     }
 
     return null;
   }
 
   public function generateURI(array $params) {
     $req_branch = false;
     $req_commit = false;
 
     $action = idx($params, 'action');
     switch ($action) {
       case 'history':
       case 'browse':
       case 'change':
       case 'lastmodified':
       case 'tags':
       case 'branches':
       case 'lint':
       case 'pathtree':
       case 'refs':
+      case 'compare':
         break;
       case 'branch':
         // NOTE: This does not actually require a branch, and won't have one
         // in Subversion. Possibly this should be more clear.
         break;
       case 'commit':
       case 'rendering-ref':
         $req_commit = true;
         break;
       default:
         throw new Exception(
           pht(
             'Action "%s" is not a valid repository URI action.',
             $action));
     }
 
     $path     = idx($params, 'path');
     $branch   = idx($params, 'branch');
     $commit   = idx($params, 'commit');
     $line     = idx($params, 'line');
 
+    $head = idx($params, 'head');
+    $against = idx($params, 'against');
+
     if ($req_commit && !strlen($commit)) {
       throw new Exception(
         pht(
           'Diffusion URI action "%s" requires commit!',
           $action));
     }
 
     if ($req_branch && !strlen($branch)) {
       throw new Exception(
         pht(
           'Diffusion URI action "%s" requires branch!',
           $action));
     }
 
     if ($action === 'commit') {
       return $this->getCommitURI($commit);
     }
 
     if (strlen($path)) {
       $path = ltrim($path, '/');
       $path = str_replace(array(';', '$'), array(';;', '$$'), $path);
       $path = phutil_escape_uri($path);
     }
 
+    $raw_branch = $branch;
     if (strlen($branch)) {
       $branch = phutil_escape_uri_path_component($branch);
       $path = "{$branch}/{$path}";
     }
 
+    $raw_commit = $commit;
     if (strlen($commit)) {
       $commit = str_replace('$', '$$', $commit);
       $commit = ';'.phutil_escape_uri($commit);
     }
 
     if (strlen($line)) {
       $line = '$'.phutil_escape_uri($line);
     }
 
+    $query = array();
     switch ($action) {
       case 'change':
       case 'history':
       case 'browse':
       case 'lastmodified':
       case 'tags':
       case 'branches':
       case 'lint':
       case 'pathtree':
       case 'refs':
         $uri = $this->getPathURI("/{$action}/{$path}{$commit}{$line}");
         break;
+      case 'compare':
+        $uri = $this->getPathURI("/{$action}/");
+        if (strlen($head)) {
+          $query['head'] = $head;
+        } else if (strlen($raw_commit)) {
+          $query['commit'] = $raw_commit;
+        } else if (strlen($raw_branch)) {
+          $query['head'] = $raw_branch;
+        }
+
+        if (strlen($against)) {
+          $query['against'] = $against;
+        }
+        break;
       case 'branch':
         if (strlen($path)) {
           $uri = $this->getPathURI("/repository/{$path}");
         } else {
           $uri = $this->getPathURI('/');
         }
         break;
       case 'external':
         $commit = ltrim($commit, ';');
         $uri = "/diffusion/external/{$commit}/";
         break;
       case 'rendering-ref':
         // This isn't a real URI per se, it's passed as a query parameter to
         // the ajax changeset stuff but then we parse it back out as though
         // it came from a URI.
         $uri = rawurldecode("{$path}{$commit}");
         break;
     }
 
     if ($action == 'rendering-ref') {
       return $uri;
     }
 
     $uri = new PhutilURI($uri);
 
     if (isset($params['lint'])) {
       $params['params'] = idx($params, 'params', array()) + array(
         'lint' => $params['lint'],
       );
     }
 
-    if (idx($params, 'params')) {
-      $uri->setQueryParams($params['params']);
+    $query = idx($params, 'params', array()) + $query;
+
+    if ($query) {
+      $uri->setQueryParams($query);
     }
 
     return $uri;
   }
 
   public function updateURIIndex() {
     $indexes = array();
 
     $uris = $this->getURIs();
     foreach ($uris as $uri) {
       if ($uri->getIsDisabled()) {
         continue;
       }
 
       $indexes[] = $uri->getNormalizedURI();
     }
 
     PhabricatorRepositoryURIIndex::updateRepositoryURIs(
       $this->getPHID(),
       $indexes);
 
     return $this;
   }
 
   public function isTracked() {
     $status = $this->getDetail('tracking-enabled');
     $map = self::getStatusMap();
     $spec = idx($map, $status);
 
     if (!$spec) {
       if ($status) {
         $status = self::STATUS_ACTIVE;
       } else {
         $status = self::STATUS_INACTIVE;
       }
       $spec = idx($map, $status);
     }
 
     return (bool)idx($spec, 'isTracked', false);
   }
 
   public function getDefaultBranch() {
     $default = $this->getDetail('default-branch');
     if (strlen($default)) {
       return $default;
     }
 
     $default_branches = array(
       PhabricatorRepositoryType::REPOSITORY_TYPE_GIT        => 'master',
       PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL  => 'default',
     );
 
     return idx($default_branches, $this->getVersionControlSystem());
   }
 
   public function getDefaultArcanistBranch() {
     return coalesce($this->getDefaultBranch(), 'svn');
   }
 
   private function isBranchInFilter($branch, $filter_key) {
     $vcs = $this->getVersionControlSystem();
 
     $is_git = ($vcs == PhabricatorRepositoryType::REPOSITORY_TYPE_GIT);
 
     $use_filter = ($is_git);
     if (!$use_filter) {
       // If this VCS doesn't use filters, pass everything through.
       return true;
     }
 
 
     $filter = $this->getDetail($filter_key, array());
 
     // If there's no filter set, let everything through.
     if (!$filter) {
       return true;
     }
 
     // If this branch isn't literally named `regexp(...)`, and it's in the
     // filter list, let it through.
     if (isset($filter[$branch])) {
       if (self::extractBranchRegexp($branch) === null) {
         return true;
       }
     }
 
     // If the branch matches a regexp, let it through.
     foreach ($filter as $pattern => $ignored) {
       $regexp = self::extractBranchRegexp($pattern);
       if ($regexp !== null) {
         if (preg_match($regexp, $branch)) {
           return true;
         }
       }
     }
 
     // Nothing matched, so filter this branch out.
     return false;
   }
 
   public static function extractBranchRegexp($pattern) {
     $matches = null;
     if (preg_match('/^regexp\\((.*)\\)\z/', $pattern, $matches)) {
       return $matches[1];
     }
     return null;
   }
 
   public function shouldTrackRef(DiffusionRepositoryRef $ref) {
     // At least for now, don't track the staging area tags.
     if ($ref->isTag()) {
       if (preg_match('(^phabricator/)', $ref->getShortName())) {
         return false;
       }
     }
 
     if (!$ref->isBranch()) {
       return true;
     }
 
     return $this->shouldTrackBranch($ref->getShortName());
   }
 
   public function shouldTrackBranch($branch) {
     return $this->isBranchInFilter($branch, 'branch-filter');
   }
 
   public function formatCommitName($commit_identifier, $local = false) {
     $vcs = $this->getVersionControlSystem();
 
     $type_git = PhabricatorRepositoryType::REPOSITORY_TYPE_GIT;
     $type_hg = PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL;
 
     $is_git = ($vcs == $type_git);
     $is_hg = ($vcs == $type_hg);
     if ($is_git || $is_hg) {
       $name = substr($commit_identifier, 0, 12);
       $need_scope = false;
     } else {
       $name = $commit_identifier;
       $need_scope = true;
     }
 
     if (!$local) {
       $need_scope = true;
     }
 
     if ($need_scope) {
       $callsign = $this->getCallsign();
       if ($callsign) {
         $scope = "r{$callsign}";
       } else {
         $id = $this->getID();
         $scope = "R{$id}:";
       }
       $name = $scope.$name;
     }
 
     return $name;
   }
 
   public function isImporting() {
     return (bool)$this->getDetail('importing', false);
   }
 
   public function isNewlyInitialized() {
     return (bool)$this->getDetail('newly-initialized', false);
   }
 
   public function loadImportProgress() {
     $progress = queryfx_all(
       $this->establishConnection('r'),
       'SELECT importStatus, count(*) N FROM %T WHERE repositoryID = %d
         GROUP BY importStatus',
       id(new PhabricatorRepositoryCommit())->getTableName(),
       $this->getID());
 
     $done = 0;
     $total = 0;
     foreach ($progress as $row) {
       $total += $row['N'] * 4;
       $status = $row['importStatus'];
       if ($status & PhabricatorRepositoryCommit::IMPORTED_MESSAGE) {
         $done += $row['N'];
       }
       if ($status & PhabricatorRepositoryCommit::IMPORTED_CHANGE) {
         $done += $row['N'];
       }
       if ($status & PhabricatorRepositoryCommit::IMPORTED_OWNERS) {
         $done += $row['N'];
       }
       if ($status & PhabricatorRepositoryCommit::IMPORTED_HERALD) {
         $done += $row['N'];
       }
     }
 
     if ($total) {
       $ratio = ($done / $total);
     } else {
       $ratio = 0;
     }
 
     // Cap this at "99.99%", because it's confusing to users when the actual
     // fraction is "99.996%" and it rounds up to "100.00%".
     if ($ratio > 0.9999) {
       $ratio = 0.9999;
     }
 
     return $ratio;
   }
 
   /**
    * Should this repository publish feed, notifications, audits, and email?
    *
    * We do not publish information about repositories during initial import,
    * or if the repository has been set not to publish.
    */
   public function shouldPublish() {
     if ($this->isImporting()) {
       return false;
     }
 
     if ($this->getDetail('herald-disabled')) {
       return false;
     }
 
     return true;
   }
 
 
 /* -(  Autoclose  )---------------------------------------------------------- */
 
 
   public function shouldAutocloseRef(DiffusionRepositoryRef $ref) {
     if (!$ref->isBranch()) {
       return false;
     }
 
     return $this->shouldAutocloseBranch($ref->getShortName());
   }
 
   /**
    * Determine if autoclose is active for a branch.
    *
    * For more details about why, use @{method:shouldSkipAutocloseBranch}.
    *
    * @param string Branch name to check.
    * @return bool True if autoclose is active for the branch.
    * @task autoclose
    */
   public function shouldAutocloseBranch($branch) {
     return ($this->shouldSkipAutocloseBranch($branch) === null);
   }
 
   /**
    * Determine if autoclose is active for a commit.
    *
    * For more details about why, use @{method:shouldSkipAutocloseCommit}.
    *
    * @param PhabricatorRepositoryCommit Commit to check.
    * @return bool True if autoclose is active for the commit.
    * @task autoclose
    */
   public function shouldAutocloseCommit(PhabricatorRepositoryCommit $commit) {
     return ($this->shouldSkipAutocloseCommit($commit) === null);
   }
 
 
   /**
    * Determine why autoclose should be skipped for a branch.
    *
    * This method gives a detailed reason why autoclose will be skipped. To
    * perform a simple test, use @{method:shouldAutocloseBranch}.
    *
    * @param string Branch name to check.
    * @return const|null Constant identifying reason to skip this branch, or null
    *   if autoclose is active.
    * @task autoclose
    */
   public function shouldSkipAutocloseBranch($branch) {
     $all_reason = $this->shouldSkipAllAutoclose();
     if ($all_reason) {
       return $all_reason;
     }
 
     if (!$this->shouldTrackBranch($branch)) {
       return self::BECAUSE_BRANCH_UNTRACKED;
     }
 
     if (!$this->isBranchInFilter($branch, 'close-commits-filter')) {
       return self::BECAUSE_BRANCH_NOT_AUTOCLOSE;
     }
 
     return null;
   }
 
 
   /**
    * Determine why autoclose should be skipped for a commit.
    *
    * This method gives a detailed reason why autoclose will be skipped. To
    * perform a simple test, use @{method:shouldAutocloseCommit}.
    *
    * @param PhabricatorRepositoryCommit Commit to check.
    * @return const|null Constant identifying reason to skip this commit, or null
    *   if autoclose is active.
    * @task autoclose
    */
   public function shouldSkipAutocloseCommit(
     PhabricatorRepositoryCommit $commit) {
 
     $all_reason = $this->shouldSkipAllAutoclose();
     if ($all_reason) {
       return $all_reason;
     }
 
     switch ($this->getVersionControlSystem()) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         return null;
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
         break;
       default:
         throw new Exception(pht('Unrecognized version control system.'));
     }
 
     $closeable_flag = PhabricatorRepositoryCommit::IMPORTED_CLOSEABLE;
     if (!$commit->isPartiallyImported($closeable_flag)) {
       return self::BECAUSE_NOT_ON_AUTOCLOSE_BRANCH;
     }
 
     return null;
   }
 
 
   /**
    * Determine why all autoclose operations should be skipped for this
    * repository.
    *
    * @return const|null Constant identifying reason to skip all autoclose
    *   operations, or null if autoclose operations are not blocked at the
    *   repository level.
    * @task autoclose
    */
   private function shouldSkipAllAutoclose() {
     if ($this->isImporting()) {
       return self::BECAUSE_REPOSITORY_IMPORTING;
     }
 
     if ($this->getDetail('disable-autoclose', false)) {
       return self::BECAUSE_AUTOCLOSE_DISABLED;
     }
 
     return null;
   }
 
 
 /* -(  Repository URI Management  )------------------------------------------ */
 
 
   /**
    * Get the remote URI for this repository.
    *
    * @return string
    * @task uri
    */
   public function getRemoteURI() {
     return (string)$this->getRemoteURIObject();
   }
 
 
   /**
    * Get the remote URI for this repository, including credentials if they're
    * used by this repository.
    *
    * @return PhutilOpaqueEnvelope URI, possibly including credentials.
    * @task uri
    */
   public function getRemoteURIEnvelope() {
     $uri = $this->getRemoteURIObject();
 
     $remote_protocol = $this->getRemoteProtocol();
     if ($remote_protocol == 'http' || $remote_protocol == 'https') {
       // For SVN, we use `--username` and `--password` flags separately, so
       // don't add any credentials here.
       if (!$this->isSVN()) {
         $credential_phid = $this->getCredentialPHID();
         if ($credential_phid) {
           $key = PassphrasePasswordKey::loadFromPHID(
             $credential_phid,
             PhabricatorUser::getOmnipotentUser());
 
           $uri->setUser($key->getUsernameEnvelope()->openEnvelope());
           $uri->setPass($key->getPasswordEnvelope()->openEnvelope());
         }
       }
     }
 
     return new PhutilOpaqueEnvelope((string)$uri);
   }
 
 
   /**
    * Get the clone (or checkout) URI for this repository, without authentication
    * information.
    *
    * @return string Repository URI.
    * @task uri
    */
   public function getPublicCloneURI() {
     return (string)$this->getCloneURIObject();
   }
 
 
   /**
    * Get the protocol for the repository's remote.
    *
    * @return string Protocol, like "ssh" or "git".
    * @task uri
    */
   public function getRemoteProtocol() {
     $uri = $this->getRemoteURIObject();
     return $uri->getProtocol();
   }
 
 
   /**
    * Get a parsed object representation of the repository's remote URI..
    *
    * @return wild A @{class@libphutil:PhutilURI}.
    * @task uri
    */
   public function getRemoteURIObject() {
     $raw_uri = $this->getDetail('remote-uri');
     if (!strlen($raw_uri)) {
       return new PhutilURI('');
     }
 
     if (!strncmp($raw_uri, '/', 1)) {
       return new PhutilURI('file://'.$raw_uri);
     }
 
     return new PhutilURI($raw_uri);
   }
 
 
   /**
    * Get the "best" clone/checkout URI for this repository, on any protocol.
    */
   public function getCloneURIObject() {
     if (!$this->isHosted()) {
       if ($this->isSVN()) {
         // Make sure we pick up the "Import Only" path for Subversion, so
         // the user clones the repository starting at the correct path, not
         // from the root.
         $base_uri = $this->getSubversionBaseURI();
         $base_uri = new PhutilURI($base_uri);
         $path = $base_uri->getPath();
         if (!$path) {
           $path = '/';
         }
 
         // If the trailing "@" is not required to escape the URI, strip it for
         // readability.
         if (!preg_match('/@.*@/', $path)) {
           $path = rtrim($path, '@');
         }
 
         $base_uri->setPath($path);
         return $base_uri;
       } else {
         return $this->getRemoteURIObject();
       }
     }
 
     // TODO: This should be cleaned up to deal with all the new URI handling.
     $another_copy = id(new PhabricatorRepositoryQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withPHIDs(array($this->getPHID()))
       ->needURIs(true)
       ->executeOne();
 
     $clone_uris = $another_copy->getCloneURIs();
     if (!$clone_uris) {
       return null;
     }
 
     return head($clone_uris)->getEffectiveURI();
   }
 
   private function getRawHTTPCloneURIObject() {
     $uri = PhabricatorEnv::getProductionURI($this->getURI());
     $uri = new PhutilURI($uri);
 
     if ($this->isGit()) {
       $uri->setPath($uri->getPath().$this->getCloneName().'.git');
     } else if ($this->isHg()) {
       $uri->setPath($uri->getPath().$this->getCloneName().'/');
     }
 
     return $uri;
   }
 
 
   /**
    * Determine if we should connect to the remote using SSH flags and
    * credentials.
    *
    * @return bool True to use the SSH protocol.
    * @task uri
    */
   private function shouldUseSSH() {
     if ($this->isHosted()) {
       return false;
     }
 
     $protocol = $this->getRemoteProtocol();
     if ($this->isSSHProtocol($protocol)) {
       return true;
     }
 
     return false;
   }
 
 
   /**
    * Determine if we should connect to the remote using HTTP flags and
    * credentials.
    *
    * @return bool True to use the HTTP protocol.
    * @task uri
    */
   private function shouldUseHTTP() {
     if ($this->isHosted()) {
       return false;
     }
 
     $protocol = $this->getRemoteProtocol();
     return ($protocol == 'http' || $protocol == 'https');
   }
 
 
   /**
    * Determine if we should connect to the remote using SVN flags and
    * credentials.
    *
    * @return bool True to use the SVN protocol.
    * @task uri
    */
   private function shouldUseSVNProtocol() {
     if ($this->isHosted()) {
       return false;
     }
 
     $protocol = $this->getRemoteProtocol();
     return ($protocol == 'svn');
   }
 
 
   /**
    * Determine if a protocol is SSH or SSH-like.
    *
    * @param string A protocol string, like "http" or "ssh".
    * @return bool True if the protocol is SSH-like.
    * @task uri
    */
   private function isSSHProtocol($protocol) {
     return ($protocol == 'ssh' || $protocol == 'svn+ssh');
   }
 
   public function delete() {
     $this->openTransaction();
 
       $paths = id(new PhabricatorOwnersPath())
         ->loadAllWhere('repositoryPHID = %s', $this->getPHID());
       foreach ($paths as $path) {
         $path->delete();
       }
 
       queryfx(
         $this->establishConnection('w'),
         'DELETE FROM %T WHERE repositoryPHID = %s',
         id(new PhabricatorRepositorySymbol())->getTableName(),
         $this->getPHID());
 
       $commits = id(new PhabricatorRepositoryCommit())
         ->loadAllWhere('repositoryID = %d', $this->getID());
       foreach ($commits as $commit) {
         // note PhabricatorRepositoryAuditRequests and
         // PhabricatorRepositoryCommitData are deleted here too.
         $commit->delete();
       }
 
       $uris = id(new PhabricatorRepositoryURI())
         ->loadAllWhere('repositoryPHID = %s', $this->getPHID());
       foreach ($uris as $uri) {
         $uri->delete();
       }
 
       $ref_cursors = id(new PhabricatorRepositoryRefCursor())
         ->loadAllWhere('repositoryPHID = %s', $this->getPHID());
       foreach ($ref_cursors as $cursor) {
         $cursor->delete();
       }
 
       $conn_w = $this->establishConnection('w');
 
       queryfx(
         $conn_w,
         'DELETE FROM %T WHERE repositoryID = %d',
         self::TABLE_FILESYSTEM,
         $this->getID());
 
       queryfx(
         $conn_w,
         'DELETE FROM %T WHERE repositoryID = %d',
         self::TABLE_PATHCHANGE,
         $this->getID());
 
       queryfx(
         $conn_w,
         'DELETE FROM %T WHERE repositoryID = %d',
         self::TABLE_SUMMARY,
         $this->getID());
 
       $result = parent::delete();
 
     $this->saveTransaction();
     return $result;
   }
 
   public function isGit() {
     $vcs = $this->getVersionControlSystem();
     return ($vcs == PhabricatorRepositoryType::REPOSITORY_TYPE_GIT);
   }
 
   public function isSVN() {
     $vcs = $this->getVersionControlSystem();
     return ($vcs == PhabricatorRepositoryType::REPOSITORY_TYPE_SVN);
   }
 
   public function isHg() {
     $vcs = $this->getVersionControlSystem();
     return ($vcs == PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL);
   }
 
   public function isHosted() {
     return (bool)$this->getDetail('hosting-enabled', false);
   }
 
   public function setHosted($enabled) {
     return $this->setDetail('hosting-enabled', $enabled);
   }
 
   public function canServeProtocol($protocol, $write) {
     if (!$this->isTracked()) {
       return false;
     }
 
     $clone_uris = $this->getCloneURIs();
     foreach ($clone_uris as $uri) {
       if ($uri->getBuiltinProtocol() !== $protocol) {
         continue;
       }
 
       $io_type = $uri->getEffectiveIoType();
       if ($io_type == PhabricatorRepositoryURI::IO_READWRITE) {
         return true;
       }
 
       if (!$write) {
         if ($io_type == PhabricatorRepositoryURI::IO_READ) {
           return true;
         }
       }
     }
 
     return false;
   }
 
   public function hasLocalWorkingCopy() {
     try {
       self::assertLocalExists();
       return true;
     } catch (Exception $ex) {
       return false;
     }
   }
 
   /**
    * Raise more useful errors when there are basic filesystem problems.
    */
   private function assertLocalExists() {
     if (!$this->usesLocalWorkingCopy()) {
       return;
     }
 
     $local = $this->getLocalPath();
     Filesystem::assertExists($local);
     Filesystem::assertIsDirectory($local);
     Filesystem::assertReadable($local);
   }
 
   /**
    * Determine if the working copy is bare or not. In Git, this corresponds
    * to `--bare`. In Mercurial, `--noupdate`.
    */
   public function isWorkingCopyBare() {
     switch ($this->getVersionControlSystem()) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         return false;
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
         $local = $this->getLocalPath();
         if (Filesystem::pathExists($local.'/.git')) {
           return false;
         } else {
           return true;
         }
     }
   }
 
   public function usesLocalWorkingCopy() {
     switch ($this->getVersionControlSystem()) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         return $this->isHosted();
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         return true;
     }
   }
 
   public function getHookDirectories() {
     $directories = array();
     if (!$this->isHosted()) {
       return $directories;
     }
 
     $root = $this->getLocalPath();
 
     switch ($this->getVersionControlSystem()) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
         if ($this->isWorkingCopyBare()) {
           $directories[] = $root.'/hooks/pre-receive-phabricator.d/';
         } else {
           $directories[] = $root.'/.git/hooks/pre-receive-phabricator.d/';
         }
         break;
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         $directories[] = $root.'/hooks/pre-commit-phabricator.d/';
         break;
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         // NOTE: We don't support custom Mercurial hooks for now because they're
         // messy and we can't easily just drop a `hooks.d/` directory next to
         // the hooks.
         break;
     }
 
     return $directories;
   }
 
   public function canDestroyWorkingCopy() {
     if ($this->isHosted()) {
       // Never destroy hosted working copies.
       return false;
     }
 
     $default_path = PhabricatorEnv::getEnvConfig(
       'repository.default-local-path');
     return Filesystem::isDescendant($this->getLocalPath(), $default_path);
   }
 
   public function canUsePathTree() {
     return !$this->isSVN();
   }
 
   public function canUseGitLFS() {
     if (!$this->isGit()) {
       return false;
     }
 
     if (!$this->isHosted()) {
       return false;
     }
 
     // TODO: Unprototype this feature.
     if (!PhabricatorEnv::getEnvConfig('phabricator.show-prototypes')) {
       return false;
     }
 
     return true;
   }
 
   public function getGitLFSURI($path = null) {
     if (!$this->canUseGitLFS()) {
       throw new Exception(
         pht(
           'This repository does not support Git LFS, so Git LFS URIs can '.
           'not be generated for it.'));
     }
 
     $uri = $this->getRawHTTPCloneURIObject();
     $uri = (string)$uri;
     $uri = $uri.'/'.$path;
 
     return $uri;
   }
 
   public function canMirror() {
     if ($this->isGit() || $this->isHg()) {
       return true;
     }
 
     return false;
   }
 
   public function canAllowDangerousChanges() {
     if (!$this->isHosted()) {
       return false;
     }
 
     // In Git and Mercurial, ref deletions and rewrites are dangerous.
     // In Subversion, editing revprops is dangerous.
 
     return true;
   }
 
   public function shouldAllowDangerousChanges() {
     return (bool)$this->getDetail('allow-dangerous-changes');
   }
 
   public function writeStatusMessage(
     $status_type,
     $status_code,
     array $parameters = array()) {
 
     $table = new PhabricatorRepositoryStatusMessage();
     $conn_w = $table->establishConnection('w');
     $table_name = $table->getTableName();
 
     if ($status_code === null) {
       queryfx(
         $conn_w,
         'DELETE FROM %T WHERE repositoryID = %d AND statusType = %s',
         $table_name,
         $this->getID(),
         $status_type);
     } else {
       // If the existing message has the same code (e.g., we just hit an
       // error and also previously hit an error) we increment the message
       // count. This allows us to determine how many times in a row we've
       // run into an error.
 
       // NOTE: The assignments in "ON DUPLICATE KEY UPDATE" are evaluated
       // in order, so the "messageCount" assignment must occur before the
       // "statusCode" assignment. See T11705.
 
       queryfx(
         $conn_w,
         'INSERT INTO %T
           (repositoryID, statusType, statusCode, parameters, epoch,
             messageCount)
           VALUES (%d, %s, %s, %s, %d, %d)
           ON DUPLICATE KEY UPDATE
             messageCount =
               IF(
                 statusCode = VALUES(statusCode),
                 messageCount + VALUES(messageCount),
                 VALUES(messageCount)),
             statusCode = VALUES(statusCode),
             parameters = VALUES(parameters),
             epoch = VALUES(epoch)',
         $table_name,
         $this->getID(),
         $status_type,
         $status_code,
         json_encode($parameters),
         time(),
         1);
     }
 
     return $this;
   }
 
   public static function assertValidRemoteURI($uri) {
     if (trim($uri) != $uri) {
       throw new Exception(
         pht('The remote URI has leading or trailing whitespace.'));
     }
 
     $uri_object = new PhutilURI($uri);
     $protocol = $uri_object->getProtocol();
 
     // Catch confusion between Git/SCP-style URIs and normal URIs. See T3619
     // for discussion. This is usually a user adding "ssh://" to an implicit
     // SSH Git URI.
     if ($protocol == 'ssh') {
       if (preg_match('(^[^:@]+://[^/:]+:[^\d])', $uri)) {
         throw new Exception(
           pht(
             "The remote URI is not formatted correctly. Remote URIs ".
             "with an explicit protocol should be in the form ".
             "'%s', not '%s'. The '%s' syntax is only valid in SCP-style URIs.",
             'proto://domain/path',
             'proto://domain:/path',
             ':/path'));
       }
     }
 
     switch ($protocol) {
       case 'ssh':
       case 'http':
       case 'https':
       case 'git':
       case 'svn':
       case 'svn+ssh':
         break;
       default:
         // NOTE: We're explicitly rejecting 'file://' because it can be
         // used to clone from the working copy of another repository on disk
         // that you don't normally have permission to access.
 
         throw new Exception(
           pht(
             'The URI protocol is unrecognized. It should begin with '.
             '"%s", "%s", "%s", "%s", "%s", "%s", or be in the form "%s".',
             'ssh://',
             'http://',
             'https://',
             'git://',
             'svn://',
             'svn+ssh://',
             'git@domain.com:path'));
     }
 
     return true;
   }
 
 
   /**
    * Load the pull frequency for this repository, based on the time since the
    * last activity.
    *
    * We pull rarely used repositories less frequently. This finds the most
    * recent commit which is older than the current time (which prevents us from
    * spinning on repositories with a silly commit post-dated to some time in
    * 2037). We adjust the pull frequency based on when the most recent commit
    * occurred.
    *
    * @param   int   The minimum update interval to use, in seconds.
    * @return  int   Repository update interval, in seconds.
    */
   public function loadUpdateInterval($minimum = 15) {
     // First, check if we've hit errors recently. If we have, wait one period
     // for each consecutive error. Normally, this corresponds to a backoff of
     // 15s, 30s, 45s, etc.
 
     $message_table = new PhabricatorRepositoryStatusMessage();
     $conn = $message_table->establishConnection('r');
     $error_count = queryfx_one(
       $conn,
       'SELECT MAX(messageCount) error_count FROM %T
         WHERE repositoryID = %d
         AND statusType IN (%Ls)
         AND statusCode IN (%Ls)',
       $message_table->getTableName(),
       $this->getID(),
       array(
         PhabricatorRepositoryStatusMessage::TYPE_INIT,
         PhabricatorRepositoryStatusMessage::TYPE_FETCH,
       ),
       array(
         PhabricatorRepositoryStatusMessage::CODE_ERROR,
       ));
 
     $error_count = (int)$error_count['error_count'];
     if ($error_count > 0) {
       return (int)($minimum * $error_count);
     }
 
     // If a repository is still importing, always pull it as frequently as
     // possible. This prevents us from hanging for a long time at 99.9% when
     // importing an inactive repository.
     if ($this->isImporting()) {
       return $minimum;
     }
 
     $window_start = (PhabricatorTime::getNow() + $minimum);
 
     $table = id(new PhabricatorRepositoryCommit());
     $last_commit = queryfx_one(
       $table->establishConnection('r'),
       'SELECT epoch FROM %T
         WHERE repositoryID = %d AND epoch <= %d
         ORDER BY epoch DESC LIMIT 1',
       $table->getTableName(),
       $this->getID(),
       $window_start);
     if ($last_commit) {
       $time_since_commit = ($window_start - $last_commit['epoch']);
     } else {
       // If the repository has no commits, treat the creation date as
       // though it were the date of the last commit. This makes empty
       // repositories update quickly at first but slow down over time
       // if they don't see any activity.
       $time_since_commit = ($window_start - $this->getDateCreated());
     }
 
     $last_few_days = phutil_units('3 days in seconds');
 
     if ($time_since_commit <= $last_few_days) {
       // For repositories with activity in the recent past, we wait one
       // extra second for every 10 minutes since the last commit. This
       // shorter backoff is intended to handle weekends and other short
       // breaks from development.
       $smart_wait = ($time_since_commit / 600);
     } else {
       // For repositories without recent activity, we wait one extra second
       // for every 4 minutes since the last commit. This longer backoff
       // handles rarely used repositories, up to the maximum.
       $smart_wait = ($time_since_commit / 240);
     }
 
     // We'll never wait more than 6 hours to pull a repository.
     $longest_wait = phutil_units('6 hours in seconds');
     $smart_wait = min($smart_wait, $longest_wait);
     $smart_wait = max($minimum, $smart_wait);
 
     return (int)$smart_wait;
   }
 
 
   /**
    * Retrieve the sevice URI for the device hosting this repository.
    *
    * See @{method:newConduitClient} for a general discussion of interacting
    * with repository services. This method provides lower-level resolution of
    * services, returning raw URIs.
    *
    * @param PhabricatorUser Viewing user.
    * @param bool `true` to throw if a remote URI would be returned.
    * @param list<string> List of allowable protocols.
    * @return string|null URI, or `null` for local repositories.
    */
   public function getAlmanacServiceURI(
     PhabricatorUser $viewer,
     $never_proxy,
     array $protocols) {
 
     $service = $this->loadAlmanacService();
     if (!$service) {
       return null;
     }
 
     $bindings = $service->getActiveBindings();
     if (!$bindings) {
       throw new Exception(
         pht(
           'The Almanac service for this repository is not bound to any '.
           'interfaces.'));
     }
 
     $local_device = AlmanacKeys::getDeviceID();
 
     if ($never_proxy && !$local_device) {
       throw new Exception(
         pht(
           'Unable to handle proxied service request. This device is not '.
           'registered, so it can not identify local services. Register '.
           'this device before sending requests here.'));
     }
 
     $protocol_map = array_fuse($protocols);
 
     $uris = array();
     foreach ($bindings as $binding) {
       $iface = $binding->getInterface();
 
       // If we're never proxying this and it's locally satisfiable, return
       // `null` to tell the caller to handle it locally. If we're allowed to
       // proxy, we skip this check and may proxy the request to ourselves.
       // (That proxied request will end up here with proxying forbidden,
       // return `null`, and then the request will actually run.)
 
       if ($local_device && $never_proxy) {
         if ($iface->getDevice()->getName() == $local_device) {
           return null;
         }
       }
 
       $uri = $this->getClusterRepositoryURIFromBinding($binding);
 
       $protocol = $uri->getProtocol();
       if (empty($protocol_map[$protocol])) {
         continue;
       }
 
       $uris[] = $uri;
     }
 
     if (!$uris) {
       throw new Exception(
         pht(
           'The Almanac service for this repository is not bound to any '.
           'interfaces which support the required protocols (%s).',
           implode(', ', $protocols)));
     }
 
     if ($never_proxy) {
       throw new Exception(
         pht(
           'Refusing to proxy a repository request from a cluster host. '.
           'Cluster hosts must correctly route their intracluster requests.'));
     }
 
     shuffle($uris);
     return head($uris);
   }
 
 
   /**
    * Build a new Conduit client in order to make a service call to this
    * repository.
    *
    * If the repository is hosted locally, this method may return `null`. The
    * caller should use `ConduitCall` or other local logic to complete the
    * request.
    *
    * By default, we will return a @{class:ConduitClient} for any repository with
    * a service, even if that service is on the current device.
    *
    * We do this because this configuration does not make very much sense in a
    * production context, but is very common in a test/development context
    * (where the developer's machine is both the web host and the repository
    * service). By proxying in development, we get more consistent behavior
    * between development and production, and don't have a major untested
    * codepath.
    *
    * The `$never_proxy` parameter can be used to prevent this local proxying.
    * If the flag is passed:
    *
    *   - The method will return `null` (implying a local service call)
    *     if the repository service is hosted on the current device.
    *   - The method will throw if it would need to return a client.
    *
    * This is used to prevent loops in Conduit: the first request will proxy,
    * even in development, but the second request will be identified as a
    * cluster request and forced not to proxy.
    *
    * For lower-level service resolution, see @{method:getAlmanacServiceURI}.
    *
    * @param PhabricatorUser Viewing user.
    * @param bool `true` to throw if a client would be returned.
    * @return ConduitClient|null Client, or `null` for local repositories.
    */
   public function newConduitClient(
     PhabricatorUser $viewer,
     $never_proxy = false) {
 
     $uri = $this->getAlmanacServiceURI(
       $viewer,
       $never_proxy,
       array(
         'http',
         'https',
       ));
     if ($uri === null) {
       return null;
     }
 
     $domain = id(new PhutilURI(PhabricatorEnv::getURI('/')))->getDomain();
 
     $client = id(new ConduitClient($uri))
       ->setHost($domain);
 
     if ($viewer->isOmnipotent()) {
       // If the caller is the omnipotent user (normally, a daemon), we will
       // sign the request with this host's asymmetric keypair.
 
       $public_path = AlmanacKeys::getKeyPath('device.pub');
       try {
         $public_key = Filesystem::readFile($public_path);
       } catch (Exception $ex) {
         throw new PhutilAggregateException(
           pht(
             'Unable to read device public key while attempting to make '.
             'authenticated method call within the Phabricator cluster. '.
             'Use `%s` to register keys for this device. Exception: %s',
             'bin/almanac register',
             $ex->getMessage()),
           array($ex));
       }
 
       $private_path = AlmanacKeys::getKeyPath('device.key');
       try {
         $private_key = Filesystem::readFile($private_path);
         $private_key = new PhutilOpaqueEnvelope($private_key);
       } catch (Exception $ex) {
         throw new PhutilAggregateException(
           pht(
             'Unable to read device private key while attempting to make '.
             'authenticated method call within the Phabricator cluster. '.
             'Use `%s` to register keys for this device. Exception: %s',
             'bin/almanac register',
             $ex->getMessage()),
           array($ex));
       }
 
       $client->setSigningKeys($public_key, $private_key);
     } else {
       // If the caller is a normal user, we generate or retrieve a cluster
       // API token.
 
       $token = PhabricatorConduitToken::loadClusterTokenForUser($viewer);
       if ($token) {
         $client->setConduitToken($token->getToken());
       }
     }
 
     return $client;
   }
 
   public function getPassthroughEnvironmentalVariables() {
     $env = $_ENV;
 
     if ($this->isGit()) {
       // $_ENV does not populate in CLI contexts if "E" is missing from
       // "variables_order" in PHP config. Currently, we do not require this
       // to be configured. Since it may not be, explictitly bring expected Git
       // environmental variables into scope. This list is not exhaustive, but
       // only lists variables with a known impact on commit hook behavior.
 
       // This can be removed if we later require "E" in "variables_order".
 
       $git_env = array(
         'GIT_OBJECT_DIRECTORY',
         'GIT_ALTERNATE_OBJECT_DIRECTORIES',
         'GIT_QUARANTINE_PATH',
       );
       foreach ($git_env as $key) {
         $value = getenv($key);
         if (strlen($value)) {
           $env[$key] = $value;
         }
       }
 
       $key = 'GIT_PUSH_OPTION_COUNT';
       $git_count = getenv($key);
       if (strlen($git_count)) {
         $git_count = (int)$git_count;
         $env[$key] = $git_count;
         for ($ii = 0; $ii < $git_count; $ii++) {
           $key = 'GIT_PUSH_OPTION_'.$ii;
           $env[$key] = getenv($key);
         }
       }
     }
 
     $result = array();
     foreach ($env as $key => $value) {
       // In Git, pass anything matching "GIT_*" though. Some of these variables
       // need to be preserved to allow `git` operations to work properly when
       // running from commit hooks.
       if ($this->isGit()) {
         if (preg_match('/^GIT_/', $key)) {
           $result[$key] = $value;
         }
       }
     }
 
     return $result;
   }
 
+  public function supportsBranchComparison() {
+    return $this->isGit();
+  }
+
 /* -(  Repository URIs  )---------------------------------------------------- */
 
 
   public function attachURIs(array $uris) {
     $custom_map = array();
     foreach ($uris as $key => $uri) {
       $builtin_key = $uri->getRepositoryURIBuiltinKey();
       if ($builtin_key !== null) {
         $custom_map[$builtin_key] = $key;
       }
     }
 
     $builtin_uris = $this->newBuiltinURIs();
     $seen_builtins = array();
     foreach ($builtin_uris as $builtin_uri) {
       $builtin_key = $builtin_uri->getRepositoryURIBuiltinKey();
       $seen_builtins[$builtin_key] = true;
 
       // If this builtin URI is disabled, don't attach it and remove the
       // persisted version if it exists.
       if ($builtin_uri->getIsDisabled()) {
         if (isset($custom_map[$builtin_key])) {
           unset($uris[$custom_map[$builtin_key]]);
         }
         continue;
       }
 
       // If the URI exists, make sure it's marked as not being disabled.
       if (isset($custom_map[$builtin_key])) {
         $uris[$custom_map[$builtin_key]]->setIsDisabled(false);
       }
     }
 
     // Remove any builtins which no longer exist.
     foreach ($custom_map as $builtin_key => $key) {
       if (empty($seen_builtins[$builtin_key])) {
         unset($uris[$key]);
       }
     }
 
     $this->uris = $uris;
 
     return $this;
   }
 
   public function getURIs() {
     return $this->assertAttached($this->uris);
   }
 
   public function getCloneURIs() {
     $uris = $this->getURIs();
 
     $clone = array();
     foreach ($uris as $uri) {
       if (!$uri->isBuiltin()) {
         continue;
       }
 
       if ($uri->getIsDisabled()) {
         continue;
       }
 
       $io_type = $uri->getEffectiveIoType();
       $is_clone =
         ($io_type == PhabricatorRepositoryURI::IO_READ) ||
         ($io_type == PhabricatorRepositoryURI::IO_READWRITE);
 
       if (!$is_clone) {
         continue;
       }
 
       $clone[] = $uri;
     }
 
     $clone = msort($clone, 'getURIScore');
     $clone = array_reverse($clone);
 
     return $clone;
   }
 
 
   public function newBuiltinURIs() {
     $has_callsign = ($this->getCallsign() !== null);
     $has_shortname = ($this->getRepositorySlug() !== null);
 
     $identifier_map = array(
       PhabricatorRepositoryURI::BUILTIN_IDENTIFIER_CALLSIGN => $has_callsign,
       PhabricatorRepositoryURI::BUILTIN_IDENTIFIER_SHORTNAME => $has_shortname,
       PhabricatorRepositoryURI::BUILTIN_IDENTIFIER_ID => true,
     );
 
     // If the view policy of the repository is public, support anonymous HTTP
     // even if authenticated HTTP is not supported.
     if ($this->getViewPolicy() === PhabricatorPolicies::POLICY_PUBLIC) {
       $allow_http = true;
     } else {
       $allow_http = PhabricatorEnv::getEnvConfig('diffusion.allow-http-auth');
     }
 
     $base_uri = PhabricatorEnv::getURI('/');
     $base_uri = new PhutilURI($base_uri);
     $has_https = ($base_uri->getProtocol() == 'https');
     $has_https = ($has_https && $allow_http);
 
     $has_http = !PhabricatorEnv::getEnvConfig('security.require-https');
     $has_http = ($has_http && $allow_http);
 
     // HTTP is not supported for Subversion.
     if ($this->isSVN()) {
       $has_http = false;
       $has_https = false;
     }
 
     $has_ssh = (bool)strlen(PhabricatorEnv::getEnvConfig('phd.user'));
 
     $protocol_map = array(
       PhabricatorRepositoryURI::BUILTIN_PROTOCOL_SSH => $has_ssh,
       PhabricatorRepositoryURI::BUILTIN_PROTOCOL_HTTPS => $has_https,
       PhabricatorRepositoryURI::BUILTIN_PROTOCOL_HTTP => $has_http,
     );
 
     $uris = array();
     foreach ($protocol_map as $protocol => $proto_supported) {
       foreach ($identifier_map as $identifier => $id_supported) {
         // This is just a dummy value because it can't be empty; we'll force
         // it to a proper value when using it in the UI.
         $builtin_uri = "{$protocol}://{$identifier}";
         $uris[] = PhabricatorRepositoryURI::initializeNewURI()
           ->setRepositoryPHID($this->getPHID())
           ->attachRepository($this)
           ->setBuiltinProtocol($protocol)
           ->setBuiltinIdentifier($identifier)
           ->setURI($builtin_uri)
           ->setIsDisabled((int)(!$proto_supported || !$id_supported));
       }
     }
 
     return $uris;
   }
 
 
   public function getClusterRepositoryURIFromBinding(
     AlmanacBinding $binding) {
     $protocol = $binding->getAlmanacPropertyValue('protocol');
     if ($protocol === null) {
       $protocol = 'https';
     }
 
     $iface = $binding->getInterface();
     $address = $iface->renderDisplayAddress();
 
     $path = $this->getURI();
 
     return id(new PhutilURI("{$protocol}://{$address}"))
       ->setPath($path);
   }
 
   public function loadAlmanacService() {
     $service_phid = $this->getAlmanacServicePHID();
     if (!$service_phid) {
       // No service, so this is a local repository.
       return null;
     }
 
     $service = id(new AlmanacServiceQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withPHIDs(array($service_phid))
       ->needBindings(true)
       ->needProperties(true)
       ->executeOne();
     if (!$service) {
       throw new Exception(
         pht(
           'The Almanac service for this repository is invalid or could not '.
           'be loaded.'));
     }
 
     $service_type = $service->getServiceImplementation();
     if (!($service_type instanceof AlmanacClusterRepositoryServiceType)) {
       throw new Exception(
         pht(
           'The Almanac service for this repository does not have the correct '.
           'service type.'));
     }
 
     return $service;
   }
 
   public function markImporting() {
     $this->openTransaction();
       $this->beginReadLocking();
         $repository = $this->reload();
         $repository->setDetail('importing', true);
         $repository->save();
       $this->endReadLocking();
     $this->saveTransaction();
 
     return $repository;
   }
 
 
 /* -(  Symbols  )-------------------------------------------------------------*/
 
   public function getSymbolSources() {
     return $this->getDetail('symbol-sources', array());
   }
 
   public function getSymbolLanguages() {
     return $this->getDetail('symbol-languages', array());
   }
 
 
 /* -(  Staging  )------------------------------------------------------------ */
 
 
   public function supportsStaging() {
     return $this->isGit();
   }
 
 
   public function getStagingURI() {
     if (!$this->supportsStaging()) {
       return null;
     }
     return $this->getDetail('staging-uri', null);
   }
 
 
 /* -(  Automation  )--------------------------------------------------------- */
 
 
   public function supportsAutomation() {
     return $this->isGit();
   }
 
   public function canPerformAutomation() {
     if (!$this->supportsAutomation()) {
       return false;
     }
 
     if (!$this->getAutomationBlueprintPHIDs()) {
       return false;
     }
 
     return true;
   }
 
   public function getAutomationBlueprintPHIDs() {
     if (!$this->supportsAutomation()) {
       return array();
     }
     return $this->getDetail('automation.blueprintPHIDs', array());
   }
 
 
 /* -(  PhabricatorApplicationTransactionInterface  )------------------------- */
 
 
   public function getApplicationTransactionEditor() {
     return new PhabricatorRepositoryEditor();
   }
 
   public function getApplicationTransactionObject() {
     return $this;
   }
 
   public function getApplicationTransactionTemplate() {
     return new PhabricatorRepositoryTransaction();
   }
 
   public function willRenderTimeline(
     PhabricatorApplicationTransactionView $timeline,
     AphrontRequest $request) {
 
     return $timeline;
   }
 
 
 /* -(  PhabricatorPolicyInterface  )----------------------------------------- */
 
 
   public function getCapabilities() {
     return array(
       PhabricatorPolicyCapability::CAN_VIEW,
       PhabricatorPolicyCapability::CAN_EDIT,
       DiffusionPushCapability::CAPABILITY,
     );
   }
 
   public function getPolicy($capability) {
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_VIEW:
         return $this->getViewPolicy();
       case PhabricatorPolicyCapability::CAN_EDIT:
         return $this->getEditPolicy();
       case DiffusionPushCapability::CAPABILITY:
         return $this->getPushPolicy();
     }
   }
 
   public function hasAutomaticCapability($capability, PhabricatorUser $user) {
     return false;
   }
 
 
 /* -(  PhabricatorMarkupInterface  )----------------------------------------- */
 
 
   public function getMarkupFieldKey($field) {
     $hash = PhabricatorHash::digestForIndex($this->getMarkupText($field));
     return "repo:{$hash}";
   }
 
   public function newMarkupEngine($field) {
     return PhabricatorMarkupEngine::newMarkupEngine(array());
   }
 
   public function getMarkupText($field) {
     return $this->getDetail('description');
   }
 
   public function didMarkupText(
     $field,
     $output,
     PhutilMarkupEngine $engine) {
     require_celerity_resource('phabricator-remarkup-css');
     return phutil_tag(
       'div',
       array(
         'class' => 'phabricator-remarkup',
       ),
       $output);
   }
 
   public function shouldUseMarkupCache($field) {
     return true;
   }
 
 
 /* -(  PhabricatorDestructibleInterface  )----------------------------------- */
 
 
   public function destroyObjectPermanently(
     PhabricatorDestructionEngine $engine) {
 
     $phid = $this->getPHID();
 
     $this->openTransaction();
 
       $this->delete();
 
       PhabricatorRepositoryURIIndex::updateRepositoryURIs($phid, array());
 
       $books = id(new DivinerBookQuery())
         ->setViewer($engine->getViewer())
         ->withRepositoryPHIDs(array($phid))
         ->execute();
       foreach ($books as $book) {
         $engine->destroyObject($book);
       }
 
       $atoms = id(new DivinerAtomQuery())
         ->setViewer($engine->getViewer())
         ->withRepositoryPHIDs(array($phid))
         ->execute();
       foreach ($atoms as $atom) {
         $engine->destroyObject($atom);
       }
 
       $lfs_refs = id(new PhabricatorRepositoryGitLFSRefQuery())
         ->setViewer($engine->getViewer())
         ->withRepositoryPHIDs(array($phid))
         ->execute();
       foreach ($lfs_refs as $ref) {
         $engine->destroyObject($ref);
       }
 
     $this->saveTransaction();
   }
 
 
 /* -(  PhabricatorSpacesInterface  )----------------------------------------- */
 
 
   public function getSpacePHID() {
     return $this->spacePHID;
   }
 
 /* -(  PhabricatorConduitResultInterface  )---------------------------------- */
 
 
   public function getFieldSpecificationsForConduit() {
     return array(
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('name')
         ->setType('string')
         ->setDescription(pht('The repository name.')),
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('vcs')
         ->setType('string')
         ->setDescription(
           pht('The VCS this repository uses ("git", "hg" or "svn").')),
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('callsign')
         ->setType('string')
         ->setDescription(pht('The repository callsign, if it has one.')),
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('shortName')
         ->setType('string')
         ->setDescription(pht('Unique short name, if the repository has one.')),
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('status')
         ->setType('string')
         ->setDescription(pht('Active or inactive status.')),
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('isImporting')
         ->setType('bool')
         ->setDescription(
           pht(
             'True if the repository is importing initial commits.')),
     );
   }
 
   public function getFieldValuesForConduit() {
     return array(
       'name' => $this->getName(),
       'vcs' => $this->getVersionControlSystem(),
       'callsign' => $this->getCallsign(),
       'shortName' => $this->getRepositorySlug(),
       'status' => $this->getStatus(),
       'isImporting' => (bool)$this->isImporting(),
     );
   }
 
   public function getConduitSearchAttachments() {
     return array(
       id(new DiffusionRepositoryURIsSearchEngineAttachment())
         ->setAttachmentKey('uris'),
     );
   }
 
 }