Implement git cl set-commit --dry-run for Rietveld.

rietveld.py

 # coding: utf-8
 # Copyright (c) 2012 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.
 """Defines class Rietveld to easily access a rietveld instance.
 
 Security implications:
 
 The following hypothesis are made:
 - Rietveld enforces:
@@ skipping 260 matching lines @@
         ('patchset', str(patchset)),
         ('patch', str(patchid)),
          ('lineno', str(lineno))])
 
   def set_flag(self, issue, patchset, flag, value):
     return self.post('/%d/edit_flags' % issue, [
         ('last_patchset', str(patchset)),
         ('xsrf_token', self.xsrf_token()),
         (flag, str(value))])
 
+  def set_flags(self, issue, patchset, flags):
+    return self.post('/%d/edit_flags' % issue, [
+        ('last_patchset', str(patchset)),
+        ('xsrf_token', self.xsrf_token()),
+        ] + [(flag, str(value)) for flag, value in flags.iteritems()])
+
   def search(
       self,
       owner=None, reviewer=None,
       base=None,
       closed=None, private=None, commit=None,
       created_before=None, created_after=None,
       modified_before=None, modified_after=None,
       per_request=None, keys_only=False,
       with_messages=False):
     """Yields search results."""
@@ skipping 446 matching lines @@
                   message,
                   add_as_reviewer=False):
     logging.info('ReadOnlyRietveld: posting comment "%s" to issue %d' %
         (message, issue))
 
   def set_flag(self, issue, patchset, flag, value):  # pylint:disable=R0201
     logging.info('ReadOnlyRietveld: setting flag "%s" to "%s" for issue %d' %
         (flag, value, issue))
     ReadOnlyRietveld._local_changes.setdefault(issue, {})[flag] = value
 
+  def set_flags(self, issue, patchset, flags):
+    for flag, value in flags.iteritems():
+      self.set_flag(issue, patchset, flag, value)
+
   def trigger_try_jobs(  # pylint:disable=R0201
       self, issue, patchset, reason, clobber, revision, builders_and_tests,
       master=None, category='cq'):
     logging.info('ReadOnlyRietveld: triggering try jobs %r for issue %d' %
         (builders_and_tests, issue))
 
   def trigger_distributed_try_jobs(  # pylint:disable=R0201
       self, issue, patchset, reason, clobber, revision, masters,
       category='cq'):
     logging.info('ReadOnlyRietveld: triggering try jobs %r for issue %d' %
         (masters, issue))