Add --sup_rep support to trychange.py.

scm.py

 # Copyright (c) 2006-2009 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.
 
 """SCM-specific utility classes."""
 
 import os
 import re
 import shutil
 import subprocess
@@ skipping 644 matching lines @@
         break
       values[key] = value
     return values
 
   @staticmethod
   def GetCheckoutRoot(directory):
     """Returns the top level directory of the current repository.
 
     The directory is returned as an absolute path.
     """
+    directory = os.path.abspath(directory)
     infos = SVN.CaptureInfo(directory, print_error=False)
     cur_dir_repo_root = infos.get("Repository Root")
     if not cur_dir_repo_root:
       return None
 
     while True:
       parent = os.path.dirname(directory)
       if (SVN.CaptureInfo(parent, print_error=False).get(
               "Repository Root") != cur_dir_repo_root):
         break
       directory = parent
     return directory