Include parent commits in git graph

Ensure parent commits are printed in the git graph info to help
distinguish when git log displays last commits from different
branches directly before/after one another.

Can happen with a different branch containing a single commit,
resulting in unclear distinction between commits and branches.

Change-Id: I3a98f35229ed201b89ba7311eb7a50e4550139ef

git_upstream/tests/base.py

@@ -339,7 +339,8 @@ class BaseTestCase(testtools.TestCase):
         self.addDetail(
             'git-log-with-graph',
             text_content(self.repo.git.log(graph=True, oneline=True,
-                                           decorate=True, all=True)))
+                                           decorate=True, all=True,
+                                           parents=True)))
 
     def run_pre_script(self):
         """