Show usage string for 'git rev-parse -h'

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

builtin-rev-parse.c

@@ -426,6 +426,13 @@ static void die_no_single_rev(int quiet)
 		die("Needed a single revision");
 }
 
+static const char builtin_rev_parse_usage[] =
+"git rev-parse --parseopt [options] -- [<args>...]\n"
+"   or: git rev-parse --sq-quote [<arg>...]\n"
+"   or: git rev-parse [options] [<arg>...]\n"
+"\n"
+"Run \"git rev-parse --parseopt -h\" for more information on the first usage.";
+
 int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 {
 	int i, as_is = 0, verify = 0, quiet = 0, revs_count = 0, type = 0;
@@ -438,6 +445,9 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 	if (argc > 1 && !strcmp("--sq-quote", argv[1]))
 		return cmd_sq_quote(argc - 2, argv + 2);
 
+	if (argc > 1 && !strcmp("-h", argv[1]))
+		usage(builtin_rev_parse_usage);
+
 	prefix = setup_git_directory();
 	git_config(git_default_config, NULL);
 	for (i = 1; i < argc; i++) {