Stop defaulting unrecognized branches to master except for handful of special refs

tests/git_cl_test.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Unit tests for git_cl.py."""
 
 import os
 import StringIO
 import stat
@@ skipping 804 matching lines @@
                      git_cl.GetTargetRef('origin', 'refs/remotes/origin/lkcr',
                                          None, None))
     self.assertEqual('refs/branch-heads/123',
                      git_cl.GetTargetRef('origin',
                                          'refs/remotes/branch-heads/123',
                                          None, None))
     self.assertEqual('refs/diff/test',
                      git_cl.GetTargetRef('origin',
                                          'refs/remotes/origin/refs/diff/test',
                                          None, None))
+    self.assertEqual('refs/heads/chrome/m42',
+                     git_cl.GetTargetRef('origin',
+                                         'refs/remotes/origin/chrome/m42',
+                                         None, None))
 
     # Check target refs for user-specified target branch.
     for branch in ('branch-heads/123', 'remotes/branch-heads/123',
                    'refs/remotes/branch-heads/123'):
       self.assertEqual('refs/branch-heads/123',
                        git_cl.GetTargetRef('origin',
                                            'refs/remotes/origin/master',
                                            branch, None))
     for branch in ('origin/master', 'remotes/origin/master',
                    'refs/remotes/origin/master'):
@@ skipping 10 matching lines @@
     # Check target refs for pending prefix.
     self.assertEqual('prefix/heads/master',
                      git_cl.GetTargetRef('origin', 'refs/remotes/origin/master',
                                          None, 'prefix/'))
 
 
 if __name__ == '__main__':
   git_cl.logging.basicConfig(
       level=git_cl.logging.DEBUG if '-v' in sys.argv else git_cl.logging.ERROR)
   unittest.main()