Enable filtering for committed revisions

Summary:
engineers requested to supporting filtering by 'committed'
revisions, and I think it makes sense.

Test Plan: verified that all the three options worked

Reviewers: epriestley, btrahan, nh

Reviewed By: nh

CC: nh, wolffiex, aran

Differential Revision: https://secure.phabricator.com/D1383

src/applications/differential/controller/revisionlist/DifferentialRevisionListController.php

@@ -316,6 +316,7 @@ class DifferentialRevisionListController extends DifferentialController {
           array(
             'all'  => 'All',
             'open' => 'Open',
+            'committed' => 'Committed',
           ),
           $params['status'],
           $uri,
@@ -348,6 +349,8 @@ class DifferentialRevisionListController extends DifferentialController {
       case 'status':
         if ($params['status'] == 'open') {
           $query->withStatus(DifferentialRevisionQuery::STATUS_OPEN);
+        } elseif ($params['status'] == 'committed') {
+          $query->withStatus(DifferentialRevisionQuery::STATUS_COMMITTED);
         }
         break;
       case 'order':