remote: force completing --mirror= instead of --mirror

"git remote --mirror" is a special case. Technically it is possible to
specify --mirror without any argument. But we will get a "dangerous,
deprecated!" warning in that case.

This new parse-opt flag allows --git-completion-helper to always
complete --mirror=, ignoring the dangerous use case.

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

builtin/remote.c

@@ -168,7 +168,7 @@ static int add(int argc, const char **argv)
 		OPT_STRING('m', "master", &master, N_("branch"), N_("master branch")),
 		{ OPTION_CALLBACK, 0, "mirror", &mirror, N_("push|fetch"),
 			N_("set up remote as a mirror to push to or fetch from"),
-			PARSE_OPT_OPTARG, parse_mirror_opt },
+			PARSE_OPT_OPTARG | PARSE_OPT_COMP_ARG, parse_mirror_opt },
 		OPT_END()
 	};
 

parse-options.c

@@ -459,6 +459,8 @@ static int show_gitcomp(struct parse_opt_ctx_t *ctx,
 		default:
 			break;
 		}
+		if (opts->flags & PARSE_OPT_COMP_ARG)
+			suffix = "=";
 		printf(" --%s%s", opts->long_name, suffix);
 	}
 	fputc('\n', stdout);

parse-options.h

@@ -39,7 +39,8 @@ enum parse_opt_option_flags {
 	PARSE_OPT_NODASH = 32,
 	PARSE_OPT_LITERAL_ARGHELP = 64,
 	PARSE_OPT_SHELL_EVAL = 256,
-	PARSE_OPT_NOCOMPLETE = 512
+	PARSE_OPT_NOCOMPLETE = 512,
+	PARSE_OPT_COMP_ARG = 1024
 };
 
 struct option;
@@ -92,6 +93,9 @@ typedef int parse_opt_ll_cb(struct parse_opt_ctx_t *ctx,
  *				Useful for options with multiple parameters.
  *   PARSE_OPT_NOCOMPLETE: by default all visible options are completable
  *			   by git-completion.bash. This option suppresses that.
+ *   PARSE_OPT_COMP_ARG: this option forces to git-completion.bash to
+ *			 complete an option as --name= not --name even if
+ *			 the option takes optional argument.
  *
  * `callback`::
  *   pointer to the callback to use for OPTION_CALLBACK or