Implement auto-roll script.

tools/push-to-trunk/common_includes.py

 #!/usr/bin/env python
 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
@@ skipping 239 matching lines @@
     # Restore state.
     state_file = "%s-state.json" % self._config[PERSISTFILE_BASENAME]
     if not self._state and os.path.exists(state_file):
       self._state.update(json.loads(FileToText(state_file)))
 
     # Skip step if requirement is not met.
     if self._requires and not self._state.get(self._requires):
       return
 
     print ">>> Step %d: %s" % (self._number, self._text)
-    self.RunStep()
-
-    # Persist state.
-    TextToFile(json.dumps(self._state), state_file)
+    try:
+      return self.RunStep()
+    finally:
+      # Persist state.
+      TextToFile(json.dumps(self._state), state_file)
 
   def RunStep(self):  # pragma: no cover
     raise NotImplementedError
 
   def Retry(self, cb, retry_on=None, wait_plan=None):
     """ Retry a function.
     Params:
       cb: The function to retry.
       retry_on: A callback that takes the result of the function and returns
                 True if the function should be retried. A function throwing an
@@ skipping 274 matching lines @@
 
     state_file = "%s-state.json" % self._config[PERSISTFILE_BASENAME]
     if options.step == 0 and os.path.exists(state_file):
       os.remove(state_file)
 
     steps = []
     for (number, step_class) in enumerate(step_classes):
       steps.append(MakeStep(step_class, number, self._state, self._config,
                             options, self._side_effect_handler))
     for step in steps[options.step:]:
-      step.Run()
+      if step.Run():
+        return 1
     return 0
 
   def Run(self, args=None):
     return self.RunSteps(self._Steps(), args)