Refactor infra git libs and testing.

infra/libs/git2/commit.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 logging
+
+from infra.libs.decorators import cached_property
+
+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 Commit(object):
+  """Represents the identity of a commit in a git repo."""
+
+  def __init__(self, repo, hsh):
+    """
+    @type repo: Repo
+    """
+    assert CommitData.HASH_RE.match(hsh)
+    self._repo = repo
+    self._hsh = hsh
+
+  # Comparison & Representation
+  def __eq__(self, other):
+    return (self is other) or (
+        isinstance(other, Commit) and (
+            self.hsh == other.hsh
+        )
+    )
+
+  def __ne__(self, other):
+    return not (self == other)
+
+  def __repr__(self):
+    return 'Commit({_repo!r}, {_hsh!r})'.format(**self.__dict__)
+
+  # Accessors
+  # pylint: disable=W0212
+  repo = property(lambda self: self._repo)
+  hsh = property(lambda self: self._hsh)
+
+  # Properties
+  @cached_property
+  def data(self):
+    """Get a structured data representation of this commit."""
+    try:
+      raw_data = self.repo.run('cat-file', 'commit', self.hsh)
+    except CalledProcessError:
+      return INVALID
+    return CommitData.from_raw(raw_data)
+
+  @cached_property
+  def parent(self):
+    """Get the corresponding parent Commit() for this Commit(), or None.
+
+    If self has more than one parent, this raises an Exception.
+    """
+    parents = self.data.parents
+    if len(parents) > 1:
+      LOGGER.error('Commit %r has more than one parent!', self.hsh)
+      return INVALID
+    return self.repo.get_commit(parents[0]) if parents else None
+
+  # Methods
+  def alter(self, **kwargs):
+    """Get a new Commit which is the same as this one, except for alterations
+    specified by kwargs.
+
+    This will intern the new Commit object into the Repo.
+    """
+    return self.repo.get_commit(
+        self.repo.intern(self.data.alter(**kwargs), 'commit'))
+
+