Add more presubmit support. Add PRESUBMIT.py to depot_tools....

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.
+"""
+
+
+def CheckChangeOnUpload(input_api, output_api):
+  return RunUnitTests(input_api, output_api)
+
+
+def CheckChangeOnCommit(input_api, output_api):
+  return (RunUnitTests(input_api, output_api) +
+          input_api.canned_checks.CheckDoNotSubmit(input_api, output_api))
+
+
+def RunUnitTests(input_api, output_api):
+  import unittest
+  tests_suite = []
+  test_loader = unittest.TestLoader()
+  def LoadTests(module_name):
+    module = __import__(module_name)
+    for part in module_name.split('.')[1:]:
+      module = getattr(module, part)
+    tests_suite.extend(test_loader.loadTestsFromModule(module)._tests)
+  # List all the test modules to test here:
+  LoadTests('tests.gcl_unittest')
+  LoadTests('tests.gclient_test')
+  LoadTests('tests.presubmit_unittest')
+  LoadTests('tests.trychange_unittest')
+  unittest.TextTestRunner(verbosity=0).run(unittest.TestSuite(tests_suite))
+  # TODO(maruel): Find a way to block the check-in.
+  return []