parse-options.[ch]: revert use of "enum" for parse_options()

Revert the parse_options() prototype change in my recent
352e761388 (parse-options.[ch]: consistently use "enum
parse_opt_result", 2021-10-08) was incorrect. The parse_options()
function returns the number of argc elements that haven't been
processed, not "enum parse_opt_result".

Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

parse-options.c

@@ -860,11 +860,11 @@ int parse_options_end(struct parse_opt_ctx_t *ctx)
 	return ctx->cpidx + ctx->argc;
 }
 
-enum parse_opt_result parse_options(int argc, const char **argv,
-				    const char *prefix,
-				    const struct option *options,
-				    const char * const usagestr[],
-				    enum parse_opt_flags flags)
+int parse_options(int argc, const char **argv,
+		  const char *prefix,
+		  const struct option *options,
+		  const char * const usagestr[],
+		  enum parse_opt_flags flags)
 {
 	struct parse_opt_ctx_t ctx;
 	struct option *real_options;

parse-options.h

@@ -211,11 +211,10 @@ struct option {
  * untouched and parse_options() returns the number of options
  * processed.
  */
-enum parse_opt_result parse_options(int argc, const char **argv,
-				    const char *prefix,
-				    const struct option *options,
-				    const char * const usagestr[],
-				    enum parse_opt_flags flags);
+int parse_options(int argc, const char **argv, const char *prefix,
+		  const struct option *options,
+		  const char * const usagestr[],
+		  enum parse_opt_flags flags);
 
 NORETURN void usage_with_options(const char * const *usagestr,
 				 const struct option *options);