Show usage string for 'git log -h', 'git show -h' and 'git diff -h'

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-diff.c

@@ -218,6 +218,8 @@ static int builtin_diff_files(struct rev_info *revs, int argc, const char **argv
 			revs->max_count = 3;
 		else if (!strcmp(argv[1], "-q"))
 			options |= DIFF_SILENT_ON_REMOVED;
+		else if (!strcmp(argv[1], "-h"))
+			usage(builtin_diff_usage);
 		else
 			return error("invalid option: %s", argv[1]);
 		argv++; argc--;

builtin-log.c

@@ -27,6 +27,10 @@ static int default_show_root = 1;
 static const char *fmt_patch_subject_prefix = "PATCH";
 static const char *fmt_pretty;
 
+static const char * const builtin_log_usage =
+	"git log [<options>] [<since>..<until>] [[--] <path>...]\n"
+	"   or: git show [options] <object>...";
+
 static void cmd_log_init(int argc, const char **argv, const char *prefix,
 		      struct rev_info *rev)
 {
@@ -61,6 +65,8 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
 			rev->show_decorations = 1;
 		} else if (!strcmp(arg, "--source")) {
 			rev->show_source = 1;
+		} else if (!strcmp(arg, "-h")) {
+			usage(builtin_log_usage);
 		} else
 			die("unrecognized argument: %s", arg);
 	}