Re: [PATCH v4 1/2] hooks: allow input from stdin for commit-related hooks

From: Orgad Shaneh <orgads@gmail.com>
To: Eric Sunshine <sunshine@sunshineco.com>
Cc: Orgad Shaneh via GitGitGadget <gitgitgadget@gmail.com>,
	Git List <git@vger.kernel.org>
Subject: Re: [PATCH v4 1/2] hooks: allow input from stdin for commit-related hooks
Date: Fri, 20 Nov 2020 09:16:27 +0200	[thread overview]
Message-ID: <CAGHpTB+2SV_GZT9QBSOQLYCO4znBCToCRJ5-guWMxxuQD+aA-w@mail.gmail.com> (raw)
In-Reply-To: <CAPig+cTaV-L_m3OFw=WAUKaiLqSVvhP7fjjFbE13QStibVmRjw@mail.gmail.com>

On Fri, Nov 20, 2020 at 8:49 AM Eric Sunshine <sunshine@sunshineco.com> wrote:
>
> On Fri, Nov 20, 2020 at 1:38 AM Eric Sunshine <sunshine@sunshineco.com> wrote:
> > I do find it quite concerning that the way this series handles the
> > stdin conflict between the hook and `-F -` can break the hook silently
> > and mysteriously. How confusing for a user to write a hook which works
> > with `git commit -m msg` and `git commit -F file` but breaks silently
> > with `git commit -F -`. What is worse is that this breakage may be
> > outside the user's control. For instance, it is easy to imagine some
> > IDE passing the commit message to git-commit via stdin (using `-F -`)
> > rather than via a file (using `-F file`).
> >
> > At the very least, this change deserves a documentation update, both
> > to explain that the prepare-commit-msg hook has a valid stdin, and
> > (importantly) that it won't be able to rely upon stdin in conjunction
> > with `-F -`.
>
> What I forgot to say here was that this patch series doesn't help
> users at all if their IDE passes the commit message to git-commit via
> stdin using `-F -`. In such a case, their hook will _never_ see a
> valid stdin coming from Git, no matter what their script does. So, the
> change made by this patch series may help some users but not others,
> and this is a limitation that should be stated in the commit message
> (and perhaps mentioned in the documentation, though that may be
> difficult to do in a general way).

At least in my case, I never expect stdin to be available when running
in the IDE, so my hook is expected to use GUI anyway. I only need
stdin when the user is running git from the terminal. So all I need from
the IDE is that it doesn't pretend to be a tty while running Git.

And regarding the hook itself - the hook author should be aware that
stdin is not always a tty, and sometimes can be closed or pipe, and
write the hook in a way that handles special cases.

- Orgad