Show "show more..." link in "Local Commits" view in Differential

Summary: Javascript! Depends on D2437 to do anything useful.

Test Plan: Clicked "show more", saw more.

Reviewers: csilvers, btrahan

Reviewed By: csilvers

CC: aran

Maniphest Tasks: T1189

Differential Revision: https://secure.phabricator.com/D2438

src/applications/differential/controller/revisionview/DifferentialRevisionViewController.php

@@ -300,6 +300,7 @@ final class DifferentialRevisionViewController extends DifferentialController {
     $toc_view->setRevisionID($revision->getID());
     $toc_view->setWhitespace($whitespace);
 
+    $comment_form = null;
     if (!$viewer_is_anonymous) {
       $draft = id(new PhabricatorDraft())->loadOneWhere(
         'authorPHID = %s AND draftKey = %s',