rebase: make -v a tiny bit more verbose

To make it possible to later remove the handling of --abort from
git-rebase--interactive.sh, align the implementation in git-rebase.sh
with the former by making it a bit more verbose.

Signed-off-by: Martin von Zweigbergk <martin.von.zweigbergk@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-rebase--interactive.sh

@@ -86,20 +86,6 @@ warn () {
 	printf '%s\n' "$*" >&2
 }
 
-output () {
-	case "$verbose" in
-	'')
-		output=$("$@" 2>&1 )
-		status=$?
-		test $status != 0 && printf "%s\n" "$output"
-		return $status
-		;;
-	*)
-		"$@"
-		;;
-	esac
-}
-
 # Output the commit message for the specified commit.
 commit_message () {
 	git cat-file commit "$1" | sed "1,/^$/d"