Add searcher test to find commits when switching branches
Add searcher test to find commits when switching branches

Add test to confirm that the searcher library is capable of supporting
finding just the carried commits when switching between which upstream
branch will be tracked by supporting searching other branches or
namespaces.

Change-Id: I62d863119af91d7d8ba8be474192890530d22a8b

stackforge/git-upstream,stackforge/git-upstream