I couldn't figure out how to easily write a testcase for this, so what I did
to try it out on OSX was:
1. create a new empty app with a single window in the main nib, setting it's
title to 'Generic'.
2. copy the MainMenu.nib out of Test.app/Contents/Resources/en.lproj
3. edit the window menu to be 'English' and re-build the app
4. run the app and check that the window title of the running app was
5. copy the saved MainMenu.nib to Test.app/Contents/Resources
6. run the app and check the enu title ... 'Generic'
7. removed the copied nib
8. run the app and check the title ... 'English'
So on OSX, the order of lookup for the main nib is generic first, then
language specific ... it looks like current lookup order in gnustep-gui is
wrong, and we should probably change the gui bundle additions code to use the
lookup methods from base and get rid of the -pathForNibResource: method.