Add genre support using musicbrainz tags.

This requires this PR: alastair/python-musicbrainzngs#266

Author: aereaux

beets/autotag/mb.py

@@ -74,6 +74,8 @@ def get_message(self):
 TRACK_INCLUDES = ['artists', 'aliases']
 if 'work-level-rels' in musicbrainzngs.VALID_INCLUDES['recording']:
     TRACK_INCLUDES += ['work-level-rels', 'artist-rels']
+if 'genres' in musicbrainzngs.VALID_INCLUDES['recording']:
+    RELEASE_INCLUDES += ['genres']
 
 
 def track_url(trackid):
@@ -415,6 +417,9 @@ def album_info(release):
         first_medium = release['medium-list'][0]
         info.media = first_medium.get('format')
 
+    if release.get('genre-list'):
+        info.genre = ';'.join(g['name'] for g in release['genre-list'])
+
     info.decode()
     return info
 

docs/changelog.rst

@@ -159,6 +159,11 @@ New features:
 * :doc:`/plugins/web`: add DELETE and PATCH methods for modifying items
 * :doc:`/plugins/lyrics`: Removed LyricWiki source (shut down on 21/09/2020).
 * Added a ``--plugins`` (or ``-p``) flag to specify a list of plugins at startup.
+* Use musicbrainz genre tag api to get genre information.  This currently
+  depends on functionality that is currently unreleased in musicbrainzngs.
+  See https://github.com/alastair/python-musicbrainzngs/pull/247 and
+  https://github.com/alastair/python-musicbrainzngs/pull/266 .
+  Thanks to :user:`aereaux`.
 
 Fixes: