topic: add tests to demonstrate topic confuses the branchhead checking logic While topics are in play, we store the branchheads (which has a topic) in "branchname:topicname" format. After digging into it I found that even in the case when we should have branch heads for "bname:tname" we get heads for "bname". The tests output reflect the confusion in branch head checking logic. Next patch will be fixing the problem.

extrakey = 'topic'
changekey = '_rewrite_noise'