Split scm-specific functions out of gclient_scm.py to scm.py.

PRESUBMIT.py

 #!/usr/bin/python
 # Copyright (c) 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.
 
 """Top-level presubmit script for depot tools.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
 details on the presubmit API built into gcl.
 """
 
 UNIT_TESTS = [
   'tests.gcl_unittest',
   'tests.gclient_test',
   'tests.gclient_scm_test',
+  'tests.gclient_utils_test',
   'tests.presubmit_unittest',
   'tests.revert_unittest',
+  'tests.scm_unittest',
   'tests.trychange_unittest',
   'tests.watchlists_unittest',
 ]
 
 def CheckChangeOnUpload(input_api, output_api):
   output = []
   output.extend(input_api.canned_checks.RunPythonUnitTests(input_api,
                                                            output_api,
                                                            UNIT_TESTS))
   return output
 
 
 def CheckChangeOnCommit(input_api, output_api):
   output = []
   output.extend(input_api.canned_checks.RunPythonUnitTests(input_api,
                                                            output_api,
                                                            UNIT_TESTS))
   output.extend(input_api.canned_checks.CheckDoNotSubmit(input_api,
                                                          output_api))
   return output