Slightly reduce the cost of resolving refs

Summary: Ref T2683. By resolving the stable name earlier, we can save a resolve when viewing branch heads. This is ~100ms in Mercurial, and roughly 25% of page weight. It's less bad in Git.

Test Plan: Saw page cost go down in "Services" tab, particularly for Mercurial browse views.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T2683

Differential Revision: https://secure.phabricator.com/D9048

src/applications/diffusion/controller/DiffusionBrowseMainController.php

@@ -19,7 +19,7 @@ final class DiffusionBrowseMainController extends DiffusionBrowseController {
           'diffusion.browsequery',
           array(
             'path' => $drequest->getPath(),
-            'commit' => $drequest->getCommit(),
+            'commit' => $drequest->getStableCommitName(),
           )));
       $reason = $results->getReasonForEmptyResultSet();
       $is_file = ($reason == DiffusionBrowseResultSet::REASON_IS_FILE);