Since home_config_paths() combines two distinct functionality already
implemented by expand_user_path() and xdg_config_home(), and hides the
home config file path ~/.gitconfig. Make the code more explicit by
replacing the use of home_config_paths() with expand_user_path() and
xdg_config_home().
Signed-off-by: Paul Tan <pyokagan@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>