Re: [PATCH] alias: pass --help through to shell alias

From: Junio C Hamano <gitster@pobox.com>
Date: May 25, 2024, 00:34 UTC
Message-ID: <xmqq8qzyk9u8.fsf@gitster.g>
In-Reply-To: <20240524070623.1344636-2-iwienand@redhat.com>

Ian Wienand <iwienand@redhat.com> writes:

> In trying to make some aliases more consistent in an internal tool, I
> implemented both -h/--help in the underlying command for a shell
> alias, and was a bit surprised when "git <alias> -h" worked but "git
> <alias> --help" didn't.

Yeah, with

    alias.lg=log --oneline
    alias.lgm=!sh -c 'GIT_NOTES_REF=refs/notes/amlog git log "$@" || :' -

"git lg -h" reports the alias, "git lg --help" does the same as "git log --help", "git lgm -h" reports the alias, but "git lgm --help" refrains from doing

    sh -c 'GIT_NOTES_REF=refs/notes/amlog git log "$@" || :' - --help

and instead does the same as "git lgm -h" to report the alias.

This is a safe behaviour because the underlying command may not be prepared to see "--help" and ignore it silently in the best case, e.g.

    sh -c 'false "$@" || :' - --help

that would confuse users by being totally silent, or

    sh -c 'awk "$@" || :' - --help

that gives "awk: not an option: --help" (which is less useful than the report of alias), or even worse yet, if the underlying command does not understand "--help" and considers it something different, who knows what havoc it would wreak.

For the above reason ...

> I would propose that "--help" to a shell alias is passed through to
> the underlying command.  This way you can write aliases that act more
> like the other git commands.

... this is a dangerous thing to do unconditionally.

I wonder if we can come up with a notation to annotate aliases that do support the "--help" option that wouldn't have been used by mistake for existing aliases?