matches all letters starting with A to D (upper and lower case). This
change allows to put more artists into that bucket. E.g. artists
starting with ä or Ä and 0 to 9 and … (three dots)
Example config for overriding a bucket pattern:
bucket:
bucket_alpha: ['A - D', 'E - L', 'M - R', 'S - Z']
bucket_alpha_regex:
'A - D': ^[0-9a-dA-D…äÄ]
- spans are now tracked via a list of dicts instead of 2 lists
previously (simpler code)
- extend_year_spans() pregenerates all possible ranges at plugin setup
stage
- a BucketError is now raised if declared bucket format not accepted
