Add test for obsolete approach to track upstream

Need to ensure that for projects using an old approach, of replacing
master with a merge commit that discards the current master contents and
replaces it with upstream plus any additional branches, can be correctly
converted by git-upstream.

Change-Id: Ifa119f47d1ffa3ba119d055679e45b2518b3bf0a
Merge "Add test for obsolete approach to track upstream"