I'm not sure we want to deal with defaults about mq in rebase.

Ideally it would be great to have a way to detect the format of the current
patch before qfinish it, and then use it when qimport-ing it. This way we could
solve both this issue and the mixed styles one.
That piece of code would change in something like:
    repo.mq.qimport(repo, (), patchname=mqrebase[rev],
          git=revgitformat,rev=[str(state[rev])])
where revgitformat has been computed before the line
    repo.mq.finish(repo, mqrebase.keys())