Add --no-history option to fetch and gclient for shallow clones.

gclient_utils.py

 # 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.
 
 """Generic utils."""
 
 import codecs
 import cStringIO
 import datetime
 import logging
@@ skipping 66 matching lines @@
   else:
     components = url.rsplit('@', 1)
     if re.match(r'^\w+\@', url) and '@' not in components[0]:
       components = [url]
 
     if len(components) == 1:
       components += [None]
   return tuple(components)
 
 
+def IsGitSha(revision):
+  """Returns true if the given string is a valid hex-encoded sha"""
+  return re.match('^[a-fA-F0-9]{6,40}$', revision) is not None
+
+
 def IsDateRevision(revision):
   """Returns true if the given revision is of the form "{ ... }"."""
   return bool(revision and re.match(r'^\{.+\}$', str(revision)))
 
 
 def MakeDateRevision(date):
   """Returns a revision representing the latest revision before the given
   date."""
   return "{" + date + "}"
 
@@ skipping 1032 matching lines @@
 def DefaultIndexPackConfig(url=''):
   """Return reasonable default values for configuring git-index-pack.
 
   Experiments suggest that higher values for pack.threads don't improve
   performance."""
   cache_limit = DefaultDeltaBaseCacheLimit()
   result = ['-c', 'core.deltaBaseCacheLimit=%s' % cache_limit]
   if url in THREADED_INDEX_PACK_BLACKLIST:
     result.extend(['-c', 'pack.threads=1'])
   return result