Re: [PATCH 2/2] help: make option --help open man pages only for Git commands

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 18, 2016, 19:51 UTC
Message-ID: <xmqqy43t6ek8.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20160818185719.4909-3-ralf.thielow@gmail.com>

Ralf Thielow <ralf.thielow@gmail.com> writes:

> If option --help is passed to a Git command, we try to open
> the man page of that command.  However, we do it even for commands
> we don't know.  Make sure it is a Git command.

What the patch does is correct, I think, but the explanation may invite a false alarm. If you added a custom command git-who in your $PATH, with an appropriate documentation for git-who(1), we would still show its documentation, no?

The same comment applies to 1/2, too, in that the word "command" will be interpreted differently by different people. For example, "git co --help" and "git help co" would work, with or without 1/2 in place when you have "[alias] co = checkout", so we are calling "Git subcommands that we ship, custom commands 'git-$foo' the users have in their $PATH, and aliases the users create" collectively "command".

As long as the reader understands that definition, both the log messages of 1/2 and 2/2 _and_ the updated description for "git help" we have in 1/2 are all very clear. I do not care too much about the commit log message, but we may want to think about the documentation a bit more.

Here is what 1/2 adds to "git help" documentation:

    +Note that `git --help ...` is almost identical to `git help ...` because
    +the former is internally converted into the latter with option --command-only
    +being added.

     To display the linkgit:git[1] man page, use `git help git`.

    @@ -43,6 +44,10 @@ OPTIONS
            Prints all the available commands on the standard output. This
            option overrides any given command or guide name.

    +-c::
    +--command-only::
    +	Display help information only for commands.
    +

First, I do not think a short form is unnecessary; the users are not expected to use that form, once they started typing "git help...". If we flip the polarity and call it --exclude-guides or something, would it make it less ambiguous?

> This breaks "git <concept> --help" while "git help <concept>" still works.

I wouldn't call that a breakage; "git everyday --help" shouldn't have worked in the first place. It did something useful merely by accident ;-).

Show 29 quoted lines

> diff --git a/git.c b/git.c
> index 0f1937f..2cd2e06 100644
> --- a/git.c
> +++ b/git.c
> @@ -528,10 +528,23 @@ static void handle_builtin(int argc, const char **argv)
>  	strip_extension(argv);
>  	cmd = argv[0];
>  
> -	/* Turn "git cmd --help" into "git help cmd" */
> +	/* Turn "git cmd --help" into "git help --command-only cmd" */
>  	if (argc > 1 && !strcmp(argv[1], "--help")) {
> +		struct argv_array args;
> +		int i;
> +
>  		argv[1] = argv[0];
>  		argv[0] = cmd = "help";
> +
> +		argv_array_init(&args);
> +		for (i = 0; i < argc; i++) {
> +			argv_array_push(&args, argv[i]);
> +			if (!i)
> +				argv_array_push(&args, "--command-only");
> +		}
> +
> +		argc++;
> +		argv = argv_array_detach(&args);
>  	}
>  
>  	builtin = get_builtin(cmd);

The code does this after it:

    if (builtin)
                exit(run_builtin(...));

and returns. If we didn't get builtin, we risk leaking args.argv here, but we assume argv[0] = cmd = "help" is always a builtin, which I think is a safe assumption, so the code is OK. Static checkers that are only half intelligent may yell at you for not releasing the resources, though. I wonder if it is worth doing

    static void handle_builtin(int argc, const char **argv)
    {
            struct argv_array args = ARGV_ARRAY_INIT;
            ...
            if (argc > 1 && !strcmp(argv[1], "--help")) {
                    ...
                    argv = args.argv;
            }
            builtin = get_builtin(cmd);
            if (builtin)
                    exit(run_builtin(...));
            argv_array_clear(&args);
    }

to help unconfuse them.

By the way, I do not see these patches on gmane, public-inbox or usual suspects. Perhaps vger is having a bad day or something?