I have several widelands installations on my system with different config and data directories.
I called widelands with the --homedir and --datadir commandline parameters and find that the --homedir is ignored, the message:
Adding home directory: $HOME/.widelands_trunk was printed but no config file reading or saving and no game saving in this directory happens. widelands always tries $HOME/.widelands.
With the datadir parameter widelands searches the hard coded default paths like . and /usr/share/games/widelands before the wanted one.
While browsing through the code of src/wlapplication.cc I find a "wrong" order of functions calls and data initialization in the constructor of WLApplication. I'm not a C++ programmer so it was a little bit tricky (trial and error) to realize that m_homedir became a new value but the internal filesystem was not informed about the changes. And even if it would the config file is read before calling handle_commandline_parameters and so the wrong or no config file is found.
The same by m_default_datadirs. The value changed after! the if(m_default_datadirs) and is ignored.
I have to rearrange the code a little bit to get it work.
Maybe you find a better solution but the patch works for me.
the patch seems to be fine for me. Any objections against a merge?