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

gclient_utils.py

Index: gclient_utils.py
diff --git a/gclient_utils.py b/gclient_utils.py
index 9c62a2a5b53af41b5aedae595bda06ecc61b1b77..f0d8cec6f49cb99637af1c11ac8e5e54d5ef8bb1 100644
--- a/gclient_utils.py
+++ b/gclient_utils.py
@@ -84,6 +84,11 @@ def SplitUrlRevision(url):
   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)))