Commit 7c7cb2a98907d99ca86bdbfca0bf9c48bfa4ed49
2018-01-20T15:53:09
Match extlang subtags If the second subtag of a BCP 47 tag is three letters long, it denotes an extended language. The tag converter ignores the language subtag and uses the extended language instead. There are some grandfathered exceptions, which are handled earlier.