cherry-pick: show commit name instead of sha1

cherry-pick: show commit name instead of sha1

When we have a conflict, we advise the user to do:

  git commit -c $sha1

This works fine, but is unnecessarily confusing and annoying
for the user to type, when:

  git commit -c $the_thing_you_called_cherry_pick_with

works just as well.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>