Re: Running 'git worktree add' in 'pre-commit' hook

[Bryan Turner <bturner@atlassian.com>]

On Tue, May 14, 2019 at 7:53 AM Cosmin Polifronie <oppturbv@gmail.com> wrote:
>
> Hello! I am trying to run 'git worktree add <path> HEAD' in the
> 'pre-commit' hook, more specifically in a Python script that is being
> called from the hook. When doing so, I am greeted with the following
> error:
>
> On Windows 10:
> Preparing worktree (detached HEAD cbfef18)
> fatal: Unable to create 'C:/Users/meh/Desktop/abc/.git/index.lock': No
> such file or directory
>
> On Arch Linux:
> Preparing worktree (detached HEAD cbfef18)
> fatal: Unable to create '/home/cosmin/Downloads/abc/.git/index.lock':
> Not a directory
>
> Is it forbidden to call this command from a hook? If yes, what kind of
> alternatives do I have? I need to make a copy of the repo in its HEAD
> state, process it and then decide if I will pass the current commit or
> not.

I can't speak to whether `git worktree add` should succeed or fail
inside a `pre-commit` hook, but...

Why do you need a new work tree, versus whatever working copy you're
running `git commit` in? Is there a reason whatever validation needs
to be done can't be done in the existing working copy? `HEAD` is the
_previous, existing commit_, not the new, currently-being-created
commit, so your validation in the new work tree, if you actually
managed to create one, would be applied to the _latest existing
commit_, not the new changes you're trying to commit. Even trying to
copy the changes over wouldn't necessarily result in the same state,
because there may be unstaged changes.

What type of validation are you trying to do? I think the failure
you're running into is an alarm bell indicating what you're trying to
do may not make sense. However, without any insight into what "process
it and then decide if I will pass the current commit or not" actually
looks like, it's hard to offer you much help.

Bryan

>
> Thanks! :)