When using git-rebase-update, pass -n to git commit.

git_common.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.
 
 # Monkeypatch IMapIterator so that Ctrl-C can kill everything properly.
 # Derived from https://gist.github.com/aljungberg/626518
 import multiprocessing.pool
 from multiprocessing.pool import IMapIterator
 def wrapper(func):
   def wrap(self, timeout=None):
@@ skipping 638 matching lines @@
   if log_msg:
     log_msg += '\n'
   log_msg += run('log', '--reverse', '--format=%H%n%B', '%s..HEAD' % merge_base)
   run('reset', '--soft', merge_base)
 
   if not get_dirty_files():
     # Sometimes the squash can result in the same tree, meaning that there is
     # nothing to commit at this point.
     print 'Nothing to commit; squashed branch is empty'
     return False
-  run('commit', '-a', '-F', '-', indata=log_msg)
+  run('commit', '--no-verify', '-a', '-F', '-', indata=log_msg)
   return True
 
 
 def tags(*args):
   return run('tag', *args).splitlines()
 
 
 def thaw():
   took_action = False
   for sha in (s.strip() for s in run_stream('rev-list', 'HEAD').xreadlines()):
@@ skipping 139 matching lines @@
         hash=branch_hash, upstream=upstream_branch, ahead=ahead, behind=behind)
 
   # Set None for upstreams which are not branches (e.g empty upstream, remotes
   # and deleted upstream branches).
   missing_upstreams = {}
   for info in info_map.values():
     if info.upstream not in info_map and info.upstream not in missing_upstreams:
       missing_upstreams[info.upstream] = None
 
   return dict(info_map.items() + missing_upstreams.items())