Re: GIT_DIR unset in vc-git.el

[Eli Zaretskii]

> From: Emre Yolcu <mail@emreyolcu.com>
> Date: Mon, 29 Apr 2024 13:17:15 -0400
> 
> Hi,
> 
> In vc-git.el, the function vc-git--call unsets GIT_DIR before calling git.  
> What is the reason for this? I am curious because I use a bare Git  
> repository to manage my home directory, and this involves temporarily  
> modifying GIT_DIR and GIT_WORK_TREE. More specifically, I use the function  
> below, which keeps a modified environment for the duration of the  
> recursive edit.
> 
>    (defun git-link-home ()
>      (interactive)
>      (let ((process-environment
>             `(,(format "GIT_DIR=%s" (expand-file-name "~/.home.git/"))
>               ,(format "GIT_WORK_TREE=%s" (expand-file-name "~/"))
>               ,@process-environment)))
>        (recursive-edit)))
> 
> This works fine for Magit, but not for VC. In particular, the Git branch  
> information that is displayed in the mode line disappears because VC  
> unsets GIT_DIR before calling git. Is there any harm in changing  
> vc-git--call to not do that?

See bug#23769 for the reasons why we remove GIT_DIR from the
environment.