You can customize the /usr/local/bin/git_init_script by supplying another file in the domain specific or server specific tree. The File["/usr/local/bin/git_init_script"] resource polls the following sources, and uses the first hit it encounters:

By default, the bash script that comes with the module is used. Customizing the git_init_script bash script requires you to supply the script at either the first (domain-specific) or the second (server specific) location.