Factor out gcl.GetRepositoryRoot() into scm.SVN.GetCheckoutRoot()

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 subprocess
 import sys
@@ skipping 468 matching lines @@
 
     while True:
       key = ReadOneItem('K')
       if not key:
         break
       value = ReadOneItem('V')
       if not value:
         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.
+    """
+    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