From: Alex Vallée <avallee@google.com>
Date: Wed, 29 Jan 2014 21:42:00 GMT
Subject: Bug: Branch rename breaks local downstream branches
Message-ID: <CAJwg7ssT-BQe+tmRNvhmPgZUsAnA8+jkuU6P-vuMdJPAOwgLMw@mail.gmail.com>

When tracking a local branch, renaming the tracked branch will not
update the downstream branch.

See transcript:

    avallee@gust:/tmp/repo (master)$ git co -b foo
    Switched to branch 'foo'
    avallee@gust:/tmp/repo (foo)$ git co -b bar --track
    Branch bar set up to track local branch foo.
    Switched to a new branch 'bar'
    avallee@gust:/tmp/repo (bar)$ git branch foo -m baz
    avallee@gust:/tmp/repo (bar)$ git co bar
    Already on 'bar'
    Your branch is based on 'foo', but the upstream is gone.
      (use "git branch --unset-upstream" to fixup)
    avallee@gust:/tmp/repo (bar)$