Refactor infra git libs and testing.

infra/libs/git2/git2.py

Index: infra/libs/git2/git2.py
diff --git a/infra/services/gnumbd/support/git.py b/infra/libs/git2/git2.py
similarity index 94%
rename from infra/services/gnumbd/support/git.py
rename to infra/libs/git2/git2.py
index b337ac20c4a65e682839ac350a1f56d5783eb255..3dfdafae7097fc1f07595a759f243b540c023407 100644
--- a/infra/services/gnumbd/support/git.py
+++ b/infra/libs/git2/git2.py
@@ -10,28 +10,14 @@ 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()
+LOGGER = logging.getLogger(__name__)
 
 
 class Repo(object):
@@ -50,6 +36,10 @@ class Repo(object):
     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