Restrict MBSync to specific fields

[eramdam]

My use case is being able to grab the "genre" field from MusicBrainz on releases that have a corresponding release group id. The MBSync seems perfect for that except that it wants to overwrite all the fields that differ between MusicBrainz and my library which causes some issues in some specific cases (Japanese kana vs Romaji or aliases etc etc).

It feels like this isn't possible yet and I feel like a '-f' option that's used to decide what fields to overwrite with MusicBrainz data could be great here. Otherwise I basically to write a script to query the MB API myself to manually modify the genre fields using the data from there which feels like wasted work because beets is uniquely equipped to do that efficiently :)