home_config_paths(): let the caller ignore xdg path
The caller can signal that it is not interested in learning
the location of $HOME/.gitconfig by passing global=NULL, but
there is no way to decline the path to the configuration
file based on $XDG_CONFIG_HOME.
Allow the caller to pass xdg=NULL to signal that it is not
interested in the XDG location.
Commit-message-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>