Comment: | Refine the semantics of codeMap.
The targets of mapped language code pairs are now disallowed, unless they are also mapped to something else.
The previous behaviour caused problems with for example sync-group, which loops over all language codes.
If we had mapping no (MW) -> nb (PROJECT), we would essentially import nb (PROJECT) messages as no (MW)
and also as nb (MW), because nb was not mapped to anything, thus resulting the code itself. |