Add git subtree daemon service.

infra/libs/git2/ref.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.
 
 from infra.libs.git2.util import CalledProcessError
 from infra.libs.git2.util import INVALID
 
 class Ref(object):
   """Represents a single simple ref in a git Repo."""
   def __init__(self, repo, ref_str):
     """
     @type repo: Repo
     @type ref_str: str
     """
     self._repo = repo
     self._ref = ref_str
 
   # Comparison & Representation
   def __eq__(self, other):
     return (self is other) or (
         isinstance(other, Ref) and (
             self.ref == other.ref and
             self.repo is other.repo
         )
     )
 
   def __ne__(self, other):
     return not (self == other)
 
+  def __hash__(self):
+    return hash((self._repo, self._ref))
+
   def __repr__(self):
     return 'Ref({_repo!r}, {_ref!r})'.format(**self.__dict__)
 
   # Accessors
   # pylint: disable=W0212
   repo = property(lambda self: self._repo)
   ref = property(lambda self: self._ref)
 
   # Properties
   @property
@@ skipping 15 matching lines @@
     if self.commit is INVALID:
       arg = other.ref
     else:
       arg = '%s..%s' % (self.ref, other.ref)
     for hsh in self.repo.run('rev-list', '--reverse', arg).splitlines():
       yield self.repo.get_commit(hsh)
 
   def update_to(self, commit):
     """Update the local copy of the ref to |commit|."""
     self.repo.run('update-ref', self.ref, commit.hsh)