Keep modifications to GitPython objects in single module

Ensure all modifications to objects imported from GitPython are placed
in the same module within git-upstream, from which all instances are
then imported.

This ensures that for all test contexts, the modified objects are the
ones used instead of accidentally using the objects without
modifications.

Specifically this allows direct execution of the strategies unit tests
using testtools to behave as expected, as otherwise the note module is
not correctly pulled in when processing the filters.

Change-Id: I0725429d8247e657681ee1dda25cb26e3688c0d9

git_upstream/lib/note.py

@@ -15,7 +15,6 @@
 # limitations under the License.
 #
 
-from git import base
 from git import GitCommandError
 
 from git_upstream.errors import GitUpstreamError
@@ -68,7 +67,3 @@ def note_message(self, note_ref='refs/notes/commits'):
             return None
         else:
             raise e
-
-base.Object.add_note = add_note
-base.Object.append_note = append_note
-base.Object.note = note_message

git_upstream/lib/pygitcompat.py

@@ -16,6 +16,9 @@
 #
 
 import git
+from git import base
+
+from git_upstream.lib import note
 
 try:
     from git.objects.commit import Commit
@@ -119,3 +122,8 @@ if not hasattr(Commit, 'iter_items'):
     git.commit.Commit = GitUpstreamCompatCommit
 else:
     Commit.short = GitUpstreamCompatCommit.short
+
+
+base.Object.add_note = note.add_note
+base.Object.append_note = note.append_note
+base.Object.note = note.note_message