parseopt: group literal string alternatives in argument help

This formally clarifies that the "--option=" part is the same for all
alternatives.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/send-pack.c b/builtin/send-pack.c
index 4923b10..bca6ea2 100644
--- a/builtin/send-pack.c
+++ b/builtin/send-pack.c
@@ -166,7 +166,7 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 		OPT_BOOL(0, "mirror", &send_mirror, N_("mirror all refs")),
 		OPT_BOOL('f', "force", &force_update, N_("force updates")),
 		{ OPTION_CALLBACK,
-		  0, "signed", &push_cert, "yes|no|if-asked", N_("GPG sign the push"),
+		  0, "signed", &push_cert, "(yes|no|if-asked)", N_("GPG sign the push"),
 		  PARSE_OPT_OPTARG, option_parse_push_signed },
 		OPT_STRING_LIST(0, "push-option", &push_options,
 				N_("server-specific"),