rebase -m: Fix incorrect short-logs of already applied commits.

rebase -m: Fix incorrect short-logs of already applied commits.

When a topic branch is rebased, some of whose commits are already
cherry-picked upstream:

    o--X--A--B--Y    <- master
     \
      A--B--Z        <- topic

then 'git rebase -m master' would report:

    Already applied: 0001 Y
    Already applied: 0002 Y

With this fix it reports the expected:

    Already applied: 0001 A
    Already applied: 0002 B

As an added bonus, this change also avoids 'echo' of a commit message,
which might contain escapements.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>