Recheck if revision hasn't been already closed in commit parser

Summary:
If attaching a commit or checking if there are any changes takes nonzero time then the revision may be closed by someone else.

Cleaner solution would be to do it inside a transaction and mark the SELECT as FOR UPDATE but it would be blocking.

Test Plan: Patched `$should_close` to be true, reparsed an already closed commit.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3555

src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php

@@ -169,8 +169,12 @@ abstract class PhabricatorRepositoryCommitMessageParserWorker
             $editor->setChangedByCommit($changed_by_commit);
           }
 
+          // Reload revision to check if someone already didn't close it.
+          $current = id(new DifferentialRevision())->load($revision_id);
+          if ($current->getStatus() != $status_closed) {
             $editor->setMessage($message)->save();
           }
+        }
 
       }
     }