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

[Eric Sunshine <sunshine@sunshineco.com>]

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).