getting “fatal: not a git repository: '.'” when using post-update hook to execute 'git pull' on another repo

Here is the script that ultimately worked. I think the bit I was originally missing that prevented it from working remotely was the unset GIT_DIR

#!/bin/sh
cd /path/to/working-copy/ || exit
unset GIT_DIR
git pull repo branch

exec git-update-server-info

getting “fatal: not a git repository: '.'” when using post-update hook to execute 'git pull' on another repo