hg: allow usage of XDG_CONFIG_HOME/hg/hgrc Modern applications must use the following paths to store configuration files: - $XDG_CONFIG_HOME/hg/hgrc, - $HOME/.config/hg/hgrc (if XDG_CONFIG_HOME is unset or not absolute). For backward compatibility, ~/.hgrc is still created if no hgrc exist using hg config --edit. See https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html