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 07:23:12 +0200	[thread overview]
Message-ID: <CAGHpTBKHmdjqrz1ABdGUUz7AwcixU_VBy1DQzybpFizqVo8C7A@mail.gmail.com> (raw)
In-Reply-To: <CAPig+cSN=-7KWgDcXM8po44PEKi27U6mJEEL0mj_wrTJBUf=WA@mail.gmail.com>

On Thu, Nov 19, 2020 at 11:23 PM Eric Sunshine <sunshine@sunshineco.com> wrote:
>
> On Thu, Nov 19, 2020 at 3:57 PM Orgad Shaneh via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
> > Let hooks receive user input if applicable.
> > [...]
> > This allows for example prompting the user to choose an issue
> > in prepare-commit-msg, and add "Fixes #123" to the commit message.
> >
> > Another possible use-case is running sanity test on pre-commit,
> > and having a prompt like "This and that issue were found in your
> > changes. Are you sure you want to commit? [Y/N]".
>
> These use-cases really help readers understand the motivation for this
> change. Good.
>
> > Allow stdin only for commit-related hooks. Some of the other
> > hooks pass their own input to the hook, so don't change them.
> >
> > Note: If pre-commit reads from stdin, and git commit is executed
> > with -F - (read message from stdin), the message is not read
> > correctly. This is fixed in the follow-up commit.
>
> Rather than making such a fundamental change and having to deal with
> the fallout by introducing complexity to handle various special-cases
> which pop up now and in the future, I wonder if it makes more sense to
> instead just update documentation to tell hook authors to read
> explicitly from the console rather than expecting stdin to be
> available (since stdin may already be consumed for other purposes when
> dealing with hooks or commands which invoke the hooks).

On the first revision I had several links in the commit message to
users who solved it this way. This solution however is not optimal.
I have a prepare-commit-msg hook that requires user interaction for
choosing an issue. This hook must work from the terminal and also
from GUI applications like IDE.

Currently the hook always pops a GUI window, but when using it
from the terminal this is inconvenient (and when running over
remote SSH without X forwarding it can't work), so I'd like it to be
usable also from the terminal.

To achieve that, I created 2 classes - one for terminal and one
for GUI, and trying to choose the correct class by checking if
stdin is a tty. The condition looks like this (Ruby):
client = STDIN.tty? ? Terminal.new : GUI.new

At this point I was surprised to discover that Git closes stdin,
so the condition is never satisfied, and I always end up with GUI.

As I mentioned, I need it to work also when executed from
GUI applications, so just reading from the console will not work
in my case. I tried other ways to detect "running from terminal"
without the tty condition, but couldn't. The environment variables
are identical when running in a GUI terminal and in the IDE.

Can you suggest an alternative way to determine if I can accept user
input from the console or not?

- Orgad