Added separate checkout and config file generation to bisect script

tools/PRESUBMIT.py

Index: tools/PRESUBMIT.py
diff --git a/tools/PRESUBMIT.py b/tools/PRESUBMIT.py
new file mode 100644
index 0000000000000000000000000000000000000000..01572314c06b789f75696cab12e3b91a9cb309fe
--- /dev/null
+++ b/tools/PRESUBMIT.py
@@ -0,0 +1,48 @@
+# Copyright (c) 2013 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 bisect trybot.
+
+See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
+details on the presubmit API built into gcl.
+"""
+
+import imp
+
+def _ExamineBisectConfigFile(input_api, output_api):
+  for f in input_api.AffectedFiles():
+    if not f.LocalPath().endswith('run-bisect-perf-regression.cfg'):
+      continue
+
+    try:
+      cfg_file = imp.load_source('config', 'run-bisect-perf-regression.cfg')
+
+      for k, v in cfg_file.config.iteritems():
+        if v:
+          return f.LocalPath()
+    except (IOError, AttributeError, TypeError):
+      return f.LocalPath()
+
+  return None
+
+def _CheckNoChangesToBisectConfigFile(input_api, output_api):
+  results = _ExamineBisectConfigFile(input_api, output_api)
+  if results:
+    return [output_api.PresubmitError(
+        'The bisection config file should only contain a config dict with '
+        'empty fields. Changes to this file should never be submitted.',
+        items=[results])]
+
+  return []
+
+def CommonChecks(input_api, output_api):
+  results = []
+  results.extend(_CheckNoChangesToBisectConfigFile(input_api, output_api))
+  return results
+
+def CheckChangeOnUpload(input_api, output_api):
+  return CommonChecks(input_api, output_api)
+
+def CheckChangeOnCommit(input_api, output_api):
+  return CommonChecks(input_api, output_api)