Don't require "branches" directory in git repo.

utils/tests/pub/test_pub.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Test infrastructure for testing pub. Unlike typical unit tests, most pub
  * tests are integration tests that stage some stuff on the file system, run
  * pub, and then validate the results. This library provides an API to build
  * tests like that.
  */
@@ skipping 295 matching lines @@
     libDir(name, value)
   ]);
 }
 
 /**
  * Describes a directory for a Git package. This directory is of the form found
  * in the repo cache of the global package cache.
  */
 DirectoryDescriptor gitPackageRepoCacheDir(String name) {
   return dir(new RegExp("$name${r'-[a-f0-9]+'}"), [
-    dir('branches'),
     dir('hooks'),
     dir('info'),
     dir('objects'),
     dir('refs')
   ]);
 }
 
 /**
  * Describes the `packages/` directory containing all the given [packages],
  * which should be name/version pairs. The packages will be validated against
@@ skipping 897 matching lines @@
 }
 
 /**
  * Schedules a callback to be called after Pub is run with [runPub], even if it
  * fails.
  */
 void _scheduleCleanup(_ScheduledEvent event) {
   if (_scheduledCleanup == null) _scheduledCleanup = [];
   _scheduledCleanup.add(event);
 }