bug#5344: 23.1.91; bug/wish: vc does not honour GIT_DIR / GIT_WORK_TREE environment variables

[Dan Nicolaescu]

Gregor Zattler <grfz@gmx.de> writes:

  > Dear emacs developers,
  > 
  > I use bare git repositories for version contol of some dotfiles.[1] This
  > means that the repository ist *not* in a .git directory which is part of
  > the working directorys hirarchy.  Instead the environment variable
  > GIT_DIR indicates the location of the repository and the environment
  > variable GIT_WORK_TREE indicates the working directory.  But in emacs/vc
  > these dotfiles do not show up as version controlled, even when the emacs
  > session inherited the correct GIT_* environment variables:
  > 
  >    ~$ export GIT_DIR=~/.fgits/emacs.git
  >    ~$ export GIT_WORK_TREE="$GIT_DIR/$(git config --get core.worktree)"
  >    ~$ printenv|grep GIT
  >    GIT_DIR=/home/grfz/.fgits/emacs.git
  >    GIT_WORK_TREE=/home/grfz/.fgits/emacs.git/../../

If you want to add support for this, it's quite likely that the only
thing that needs to be changed is the vc-git-root in
emacs/lisp/vc-git.el.