Add AlbumInfo.data_url property, populate it for Discogs matches and display it when it is non-empty.

Makes it easier for people to find the best Discogs (or other) match
and import it to Music Brainz using a grease monkey or similar script.

beets/autotag/hooks.py

@@ -52,6 +52,7 @@ class AlbumInfo(object):
     - ``albumdisambig``: MusicBrainz release disambiguation comment
     - ``artist_credit``: Release-specific artist name
     - ``data_source``: The original data source (MusicBrainz, Discogs, etc.)
+    - ``data_url``: The data source release URL.
 
     The fields up through ``tracks`` are required. The others are
     optional and may be None.
@@ -62,7 +63,8 @@ class AlbumInfo(object):
                  releasegroup_id=None, catalognum=None, script=None,
                  language=None, country=None, albumstatus=None, media=None,
                  albumdisambig=None, artist_credit=None, original_year=None,
-                 original_month=None, original_day=None, data_source=None):
+                 original_month=None, original_day=None, data_source=None,
+                 data_url=None):
         self.album = album
         self.album_id = album_id
         self.artist = artist
@@ -90,6 +92,7 @@ class AlbumInfo(object):
         self.original_month = original_month
         self.original_day = original_day
         self.data_source = data_source or 'Unknown'
+        self.data_url = data_url
 
     # Work around a bug in python-musicbrainz-ngs that causes some
     # strings to be bytes rather than Unicode.

beets/ui/commands.py

@@ -216,6 +216,10 @@ def show_change(cur_artist, cur_album, match):
             message += u' %s' % ui.colorize('yellow', PARTIAL_MATCH_MESSAGE)
         print_(message)
 
+    # Data URL.
+    if match.info.data_url:
+        print_('URL:\n    %s' % match.info.data_url)
+
     # Info line.
     info = []
     info.append('(Similarity: %s)' % dist_string(match.distance))

beetsplug/discogs.py

@@ -91,6 +91,7 @@ class DiscogsPlugin(BeetsPlugin):
             catalogno = None
         country = result.data.get('country')
         media = result.data['formats'][0]['name']
+        data_url = result.data['uri']
         return AlbumInfo(album, album_id, artist, artist_id, tracks, asin=None,
                          albumtype=albumtype, va=va, year=year, month=None,
                          day=None, label=label, mediums=mediums,
@@ -99,7 +100,8 @@ class DiscogsPlugin(BeetsPlugin):
                          country=country, albumstatus=None, media=media,
                          albumdisambig=None, artist_credit=None,
                          original_year=None, original_month=None,
-                         original_day=None, data_source='Discogs')
+                         original_day=None, data_source='Discogs',
+                         data_url=data_url)
 
     def get_artist(self, artists):
         """Returns an artist string (all artists) and an artist_id (the main