remote: improve argument help for add --mirror

Group the possible values using a pair of parentheses and don't mark
them for translation, as they are literal strings that have to be used
as-is in any locale.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/remote.c b/builtin/remote.c
index 1a82d85..4f95d21 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -167,7 +167,7 @@ static int add(int argc, const char **argv)
 		OPT_STRING_LIST('t', "track", &track, N_("branch"),
 				N_("branch(es) to track")),
 		OPT_STRING('m', "master", &master, N_("branch"), N_("master branch")),
-		{ OPTION_CALLBACK, 0, "mirror", &mirror, N_("push|fetch"),
+		{ OPTION_CALLBACK, 0, "mirror", &mirror, "(push|fetch)",
 			N_("set up remote as a mirror to push to or fetch from"),
 			PARSE_OPT_OPTARG | PARSE_OPT_COMP_ARG, parse_mirror_opt },
 		OPT_END()