Refactor infra git libs and testing.

infra/libs/git2/git2.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.
 import collections
 import fnmatch
 import logging
 import os
 import subprocess
 import sys
 import tempfile
 import urlparse
 
-from infra.services.gnumbd.support.util import (
-    cached_property, CalledProcessError)
+from infra.libs.decorators import cached_property
 
-from infra.services.gnumbd.support.data import CommitData
+from infra.libs.git2.util import CalledProcessError
+from infra.libs.git2.util import INVALID
+from infra.libs.git2.data import CommitData
+
 
 LOGGER = logging.getLogger(__name__)
 
 
-class _Invalid(object):
-  def __call__(self, *_args, **_kwargs):
-    return self
-
-  def __getattr__(self, _key):
-    return self
-
-  def __eq__(self, _other):
-    return False
-
-  def __ne__(self, _other):  # pylint: disable=R0201
-    return True
-
-INVALID = _Invalid()
-
-
 class Repo(object):
   """Represents a remote git repo.
 
   Manages the (bare) on-disk mirror of the remote repo.
   """
   MAX_CACHE_SIZE = 1024
 
   def __init__(self, url):
     self.dry_run = False
     self.repos_dir = None
 
     self._url = url
     self._repo_path = None
     self._commit_cache = collections.OrderedDict()
     self._log = LOGGER.getChild('Repo')
 
+  def __getitem__(self, ref):
+    """Get a Ref attached to this Repo."""
+    return Ref(self, ref)
+
   def reify(self):
     """Ensures the local mirror of this Repo exists."""
     assert self.repos_dir is not None
     parsed = urlparse.urlparse(self._url)
     norm_url = parsed.netloc + parsed.path
     if norm_url.endswith('.git'):
       norm_url = norm_url[:-len('.git')]
     folder = norm_url.replace('-', '--').replace('/', '-').lower()
 
     rpath = os.path.abspath(os.path.join(self.repos_dir, folder))
@@ skipping 198 matching lines @@
 
   def fast_forward_push(self, commit):
     """Push |commit| to this ref on the remote, and update the local copy of the
     ref to |commit|."""
     self.repo.run('push', 'origin', '%s:%s' % (commit.hsh, self.ref))
     self.update_to(commit)
 
   def update_to(self, commit):
     """Update the local copy of the ref to |commit|."""
     self.repo.run('update-ref', self.ref, commit.hsh)