test-lib: fail if invalid options are passed

Previously, unknown options would be ignored, including any subsequent
valid options.

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Clemens Buchacher

t/test-lib.sh

@@ -115,7 +115,7 @@ do
 	--tee)
 		shift ;; # was handled already
 	*)
-		break ;;
+		echo "error: unknown test option '$1'" >&2; exit 1 ;;
 	esac
 done