Refactor cache-updating code to eliminate unnecessary fetches.

tests/gclient_scm_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 gclient_scm.py."""
 
 # pylint: disable=E1103
 
 # Import before super_mox to keep valid references.
 from shutil import rmtree
 from subprocess import Popen, PIPE, STDOUT
 
 import logging
 import os
 import re
 import sys
 import tempfile
 import unittest
 
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 from testing_support.super_mox import mox, StdoutCheck, SuperMoxTestBase
 from testing_support.super_mox import TestCaseUtils
 
 import gclient_scm
+import git_cache
 import subprocess2
 
+# Disable global git cache
+git_cache.Mirror.SetCachePath(None)
+
 # Shortcut since this function is used often
 join = gclient_scm.os.path.join
 
 TIMESTAMP_RE = re.compile('\[[0-9]{1,2}:[0-9]{2}:[0-9]{2}\] (.*)', re.DOTALL)
 def strip_timestamps(value):
   lines = value.splitlines(True)
   for i in xrange(len(lines)):
     m = TIMESTAMP_RE.match(lines[i])
     if m:
       lines[i] = m.group(1)
@@ skipping 1525 matching lines @@
     file_list = []
     options.revision = 'unmanaged'
     scm.update(options, (), file_list)
     self.assertEquals(file_list, expected_file_list)
     self.assertEquals(scm.revinfo(options, (), None),
                       '069c602044c5388d2d15c3f875b057c852003458')
     self.checkstdout('________ unmanaged solution; skipping .\n')
 
 
 if __name__ == '__main__':
-  if '-v' in sys.argv:
-    logging.basicConfig(
-        level=logging.DEBUG,
-        format='%(asctime).19s %(levelname)s %(filename)s:'
-               '%(lineno)s %(message)s')
+  level = logging.DEBUG if '-v' in sys.argv else logging.FATAL
+  logging.basicConfig(
+      level=level,
+      format='%(asctime).19s %(levelname)s %(filename)s:'
+             '%(lineno)s %(message)s')
   unittest.main()
 
 # vim: ts=2:sw=2:tw=80:et: