diff: use add_diff_options() in diff_opt_parse()

Prepare the removal of the parseopts member of struct diff_options by
using the API function add_diff_options() instead of accessing it
directly to get the command line option definitions.  Building the copy
by concatenating with an empty option array is slightly awkward, but
simpler than a non-concat version of add_diff_options() would be to use
in places that need concatenation.

Suggested-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: René Scharfe <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: rscharfe

diff.c

@@ -5680,15 +5680,19 @@ static void prep_parse_options(struct diff_options *options)
 int diff_opt_parse(struct diff_options *options,
 		   const char **av, int ac, const char *prefix)
 {
+	struct option no_options[] = { OPT_END() };
+	struct option *parseopts = add_diff_options(no_options, options);
+
 	if (!prefix)
 		prefix = "";
 
-	ac = parse_options(ac, av, prefix, options->parseopts, NULL,
+	ac = parse_options(ac, av, prefix, parseopts, NULL,
 			   PARSE_OPT_KEEP_DASHDASH |
 			   PARSE_OPT_KEEP_UNKNOWN_OPT |
 			   PARSE_OPT_NO_INTERNAL_HELP |
 			   PARSE_OPT_ONE_SHOT |
 			   PARSE_OPT_STOP_AT_NON_OPTION);
+	free(parseopts);
 
 	return ac;
 }