parseopt: add flag to stop on first non option

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

parse-options.c

@@ -249,6 +249,8 @@ int parse_options(int argc, const char **argv, const struct option *options,
 		const char *arg = args.argv[0];
 
 		if (*arg != '-' || !arg[1]) {
+			if (flags & PARSE_OPT_STOP_AT_NON_OPTION)
+				break;
 			argv[j++] = args.argv[0];
 			continue;
 		}