git-rebase: don't ignore unexpected command line arguments

Currently, git-rebase will silently ignore any unexpected command-line
switches and arguments (the command-line produced by git rev-parse).
This allowed the rev-parse bug, fixed in the preceding commits, to go
unnoticed.  Let's make sure that doesn't happen again.  We shouldn't be
ignoring unexpected arguments.  Let's not.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-rebase.sh

@@ -348,6 +348,9 @@ do
 		shift
 		break
 		;;
+	*)
+		usage
+		;;
 	esac
 	shift
 done