Let bot_update recipe api force usage of bot_update.

scripts/slave/recipe_modules/bot_update/api.py

 # Copyright 2014 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.
 
 
 """Recipe module to ensure a checkout is consistant on a bot."""
 
 
 from slave import recipe_api
 
@@ skipping 39 matching lines @@
   def __call__(self, name, cmd, **kwargs):
     """Wrapper for easy calling of bot_update."""
     assert isinstance(cmd, (list, tuple))
     kwargs.setdefault('abort_on_failure', True)
     bot_update_path = self.m.path['build'].join(
         'scripts', 'slave', 'bot_update.py')
     return self.m.python(name, bot_update_path, cmd, **kwargs)
 
   def ensure_checkout(self, gclient_config=None, suffix=None,
                       patch=True, ref=None, update_presentation=True,
-                      revisions=[],
-                      **kwargs):
+                      revisions=[], force=False, **kwargs):
     # We can re-use the gclient spec from the gclient module, since all the
     # data bot_update needs is already configured into the gclient spec.
     cfg = gclient_config or self.m.gclient.c
     spec_string = jsonish_to_python(cfg.as_jsonish(), True)
 
     # Used by bot_update to determine if we want to run or not.
     master = self.m.properties['mastername']
     builder = self.m.properties['buildername']
     slave = self.m.properties['slavename']
 
@@ skipping 40 matching lines @@
         ['--patchset', patchset],
         ['--patch_url', patch_url],
 
         # 4. Hookups to JSON output back into recipes.
         ['--output_json', self.m.json.output()],]
 
     # Filter out flags that are None.
     cmd = [item for flag_set in flags
            for item in flag_set if flag_set[1] is not None]
 
+    if force:
+      cmd.append('--force')
+
     # Inject Json output for testing.
     git_mode = self.m.properties.get('mastername') in GIT_MASTERS
     first_sln = cfg.solutions[0].name
     step_test_data = lambda: self.test_api.output_json(
-        master, builder, slave, root, first_sln, rev_map, git_mode)
+        master, builder, slave, root, first_sln, rev_map, git_mode, force)
 
     def followup_fn(step_result):
       if update_presentation:
         # Set properties such as got_revision.
         if 'properties' in step_result.json.output:
           properties = step_result.json.output['properties']
           for prop_name, prop_value in properties.iteritems():
             step_result.presentation.properties[prop_name] = prop_value
       # Add helpful step description in the step UI.
       if 'step_text' in step_result.json.output:
@@ skipping 14 matching lines @@
     # Set the "checkout" path for the main solution.
     # This is used by the Chromium module to figure out where to look for
     # the checkout.
     bot_update_step = self.m.step_history.last_step()
     # bot_update actually just sets root to be the folder name of the
     # first solution.
     if bot_update_step.json.output['did_run']:
       co_root = bot_update_step.json.output['root']
       cwd = kwargs.get('cwd', self.m.path['slave_build'])
       self.m.path['checkout'] = cwd.join(*co_root.split(self.m.path.sep))