oddballs: send usage() help text to standard output

Using the show_usage_if_asked() helper we introduced earlier, fix
callers of usage() that want to show the help text when explicitly
asked by the end-user.  The help text now goes to the standard
output stream for them.

The callers in this step are oddballs in that their invocations of
usage() are *not* guarded by

	if (argc == 2 && !strcmp(argv[1], "-h")
		usage(...);

There are (unnecessarily) being clever ones that do things like

	if (argc != 2 || !strcmp(argv[1], "-h")
		usage(...);

to say "I know I take only one argument, so argc != 2 is always an
error regardless of what is in argv[].  Ah, by the way, even if argc
is 2, "-h" is a request for usage text, so we do the same".

Some like "git var -h" just do not treat "-h" any specially, and let
it take the same error code paths as a parameter error.

Now we cannot do the same, so these callers are rewrittin to do the
show_usage_and_exit_if_asked() first and then handle the usage error
the way they used to.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/credential.c

@@ -18,7 +18,8 @@ int cmd_credential(int argc,
 
 	git_config(git_default_config, NULL);
 
-	if (argc != 2 || !strcmp(argv[1], "-h"))
+	show_usage_if_asked(argc, argv, usage_msg);
+	if (argc != 2)
 		usage(usage_msg);
 	op = argv[1];
 

builtin/fetch-pack.c

@@ -75,6 +75,8 @@ int cmd_fetch_pack(int argc,
 	list_objects_filter_init(&args.filter_options);
 	args.uploadpack = "git-upload-pack";
 
+	show_usage_if_asked(argc, argv, fetch_pack_usage);
+
 	for (i = 1; i < argc && *argv[i] == '-'; i++) {
 		const char *arg = argv[i];
 

builtin/unpack-file.c

@@ -26,15 +26,19 @@ static char *create_temp_file(struct object_id *oid)
 	return path;
 }
 
+static const char usage_msg[] =
+"git unpack-file <blob>";
+
 int cmd_unpack_file(int argc,
 		    const char **argv,
 		    const char *prefix UNUSED,
 		    struct repository *repo UNUSED)
 {
 	struct object_id oid;
 
-	if (argc != 2 || !strcmp(argv[1], "-h"))
-		usage("git unpack-file <blob>");
+	show_usage_if_asked(argc, argv, usage_msg);
+	if (argc != 2)
+		usage(usage_msg);
 	if (repo_get_oid(the_repository, argv[1], &oid))
 		die("Not a valid object name %s", argv[1]);
 

builtin/upload-archive.c

@@ -27,7 +27,8 @@ int cmd_upload_archive_writer(int argc,
 	const char *arg_cmd = "argument ";
 	int ret;
 
-	if (argc != 2 || !strcmp(argv[1], "-h"))
+	show_usage_if_asked(argc, argv, upload_archive_usage);
+	if (argc != 2)
 		usage(upload_archive_usage);
 
 	if (!enter_repo(argv[1], 0))

builtin/var.c

@@ -221,6 +221,7 @@ int cmd_var(int argc,
 	const struct git_var *git_var;
 	char *val;
 
+	show_usage_if_asked(argc, argv, var_usage);
 	if (argc != 2)
 		usage(var_usage);