Improve rendering of history graph in "CommitGraphView"

Summary: Ref T13552. In the new combined "table/list" graph view, tidy up the graph rendering.

Test Plan: {F7633504}

Maniphest Tasks: T13552

Differential Revision: https://secure.phabricator.com/D21411

src/infrastructure/diff/view/PHUIDiffGraphView.php

@@ -205,6 +205,7 @@ final class PHUIDiffGraphView extends Phobject {
       'diffusion-commit-graph',
       array(
         'count' => $count,
+        'autoheight' => true,
       ));
 
     return $graph;