Show usage string for 'git show-ref -h'

This only changes the behavior of "git show-ref -h" without any
other options and arguments.

"show-ref -h" currently is short for "show-ref --head", which
shows all the refs/* and HEAD, as opposed to "show-ref" that
shows all the refs/* and not HEAD.

Does anybody use "show-ref -h"?  It was in Linus's original, most
likely only because "it might be handy", not because "the command
should not show the HEAD by default for such and such reasons".
So I think it is okay if "show-ref -h" (but not "show-ref
--head") gives help and exits.

If a current script uses "git show-ref -h" without any other
arguments, it would have to be adapted by changing "-h" to
"--head".

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-show-ref.txt

@@ -8,7 +8,7 @@ git-show-ref - List references in a local repository
 SYNOPSIS
 --------
 [verse]
-'git show-ref' [-q|--quiet] [--verify] [-h|--head] [-d|--dereference]
+'git show-ref' [-q|--quiet] [--verify] [--head] [-d|--dereference]
 	     [-s|--hash[=<n>]] [--abbrev[=<n>]] [--tags]
 	     [--heads] [--] <pattern>...
 'git show-ref' --exclude-existing[=<pattern>] < ref-list
@@ -30,7 +30,6 @@ the `.git` directory.
 OPTIONS
 -------
 
--h::
 --head::
 
 	Show the HEAD reference.

builtin-show-ref.c

@@ -7,7 +7,7 @@
 #include "parse-options.h"
 
 static const char * const show_ref_usage[] = {
-	"git show-ref [-q|--quiet] [--verify] [-h|--head] [-d|--dereference] [-s|--hash[=<n>]] [--abbrev[=<n>]] [--tags] [--heads] [--] [pattern*] ",
+	"git show-ref [-q|--quiet] [--verify] [--head] [-d|--dereference] [-s|--hash[=<n>]] [--abbrev[=<n>]] [--tags] [--heads] [--] [pattern*] ",
 	"git show-ref --exclude-existing[=pattern] < ref-list",
 	NULL
 };
@@ -183,7 +183,10 @@ static const struct option show_ref_options[] = {
 	OPT_BOOLEAN(0, "heads", &heads_only, "only show heads (can be combined with tags)"),
 	OPT_BOOLEAN(0, "verify", &verify, "stricter reference checking, "
 		    "requires exact ref path"),
-	OPT_BOOLEAN('h', "head", &show_head, "show the HEAD reference"),
+	{ OPTION_BOOLEAN, 'h', NULL, &show_head, NULL,
+	  "show the HEAD reference",
+	  PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
+	OPT_BOOLEAN(0, "head", &show_head, "show the HEAD reference"),
 	OPT_BOOLEAN('d', "dereference", &deref_tags,
 		    "dereference tags into object IDs"),
 	{ OPTION_CALLBACK, 's', "hash", &abbrev, "n",
@@ -201,6 +204,9 @@ static const struct option show_ref_options[] = {
 
 int cmd_show_ref(int argc, const char **argv, const char *prefix)
 {
+	if (argc == 2 && !strcmp(argv[1], "-h"))
+		usage_with_options(show_ref_usage, show_ref_options);
+
 	argc = parse_options(argc, argv, prefix, show_ref_options,
 			     show_ref_usage, PARSE_OPT_NO_INTERNAL_HELP);