rebase -i: When an 'edit' stops, mention the commit

In a rebase session where more than one commit is to be 'edit'ed, and the
user spends considerable time to 'edit' a commit, it is easy to forget what
one wanted to 'edit' at the individual commits. It would be helpful to see
at which commit the rebase stopped.

Incidentally, if the rebase stopped due to merge conflicts or other errors,
the commit was already reported ("Could not apply $sha1..."), but when
rebase stopped after successfully applying an "edit" commit, it would not
mention it. With this change the commit is reported.

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

git-rebase--interactive.sh

@@ -277,7 +277,7 @@ do_next () {
 			die_with_patch $sha1 "Could not apply $sha1... $rest"
 		make_patch $sha1
 		: > "$DOTEST"/amend
-		warn
+		warn "Stopped at $sha1... $rest"
 		warn "You can amend the commit now, with"
 		warn
 		warn "	git commit --amend"