Plugin for the audio tagger Picard MusicBrainz. The plugin sets a user defined tag TXXX:releasecompleteness if a release is complete i.e. all tracks of the release exist.
Download the file PicardReleseCompletenessTag.py
Open Picard MusicBrainz and select the file in Options/Options/Plugins/Install Plugin ...
Enable the plugin in the plugin list.