Refactor infra git libs and testing.

infra/libs/git2/data/data.py

Index: infra/libs/git2/data/data.py
diff --git a/infra/libs/git2/data/data.py b/infra/libs/git2/data/data.py
new file mode 100644
index 0000000000000000000000000000000000000000..f1a8497ce83181b4131b69cfd0fbd4aac550850e
--- /dev/null
+++ b/infra/libs/git2/data/data.py
@@ -0,0 +1,24 @@
+# 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.
+
+
+################################################################################
+# Base Class
+################################################################################
+
+class Alterable(object):
+  def to_dict(self):  # pragma: no cover
+    """The shallow dictionary representation of this object (i.e. the dictionary
+    may contain Alterable instances as values)."""
+    raise NotImplementedError()
+
+  def alter(self, **kwargs):  # pragma: no cover
+    """Returns a copy of self, except with the fields listed in kwargs replaced
+    with new values."""
+    raise NotImplementedError()
+
+  @classmethod
+  def from_raw(cls, data):  # pragma: no cover
+    """Construct an instance of this class from a string."""
+    raise NotImplementedError()