Code review comment for lp:~widelands-dev/widelands/add-xdg-support

Added a log entry for the configuration file if it's outside the home directory.

The homedir already gets logged and if a folder gets added through XDG_DATA_DIRS it's mentioned as "Adding directory: /usr/share/widelands".

The argument --homedir overrides the configuration directory and sets it to the given homedir.
The argument --datadir takes precedence over XDG_DATA_DIRS while the environment variable itself takes precedence over the INSTALL_DATADIR path given at compile time.