diff-parseopt: convert -s|--no-patch

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -4906,6 +4906,9 @@ static void prep_parse_options(struct diff_options *options)
 		OPT_BITOP('p', "patch", &options->output_format,
 			  N_("generate patch"),
 			  DIFF_FORMAT_PATCH, DIFF_FORMAT_NO_OUTPUT),
+		OPT_BIT_F('s', "no-patch", &options->output_format,
+			  N_("suppress diff output"),
+			  DIFF_FORMAT_NO_OUTPUT, PARSE_OPT_NONEG),
 		OPT_BITOP('u', NULL, &options->output_format,
 			  N_("generate patch"),
 			  DIFF_FORMAT_PATCH, DIFF_FORMAT_NO_OUTPUT),
@@ -4983,9 +4986,7 @@ int diff_opt_parse(struct diff_options *options,
 		return ac;
 
 	/* Output format options */
-	if (!strcmp(arg, "-s") || !strcmp(arg, "--no-patch"))
-		options->output_format |= DIFF_FORMAT_NO_OUTPUT;
-	else if (starts_with(arg, "--stat"))
+	if (starts_with(arg, "--stat"))
 		/* --stat, --stat-width, --stat-name-width, or --stat-count */
 		return stat_opt(options, av);
 	else if (!strcmp(arg, "--compact-summary")) {