Add MusicBrainz' Release Track Id tag

The Release Track Id uniquely identifies a recording on a release - that
is, even if a recording appears twice on a release (meaning that the
combination of recording and release id are not enough to figure out
which one it is), the release track id will allow differentiating the two.

The tag names are taken from
https://musicbrainz.org/doc/MusicBrainz_Picard/Tags/Mapping

NEWS

@@ -67,6 +67,7 @@ ver 0.19 (not yet released)
 * configuration
   - allow playlist directory without music directory
   - use XDG to auto-detect "music_directory" and "db_file"
+* add tag "MUSICBRAINZ_RELEASETRACKID"
 * new resampler option using libsoxr
 * ARM NEON optimizations
 * install systemd unit for socket activation

doc/mpd.conf.5

@@ -180,7 +180,8 @@ clients.  Note that you must recreate (not update) your database for changes to
 this parameter to take effect.  Possible values are artist, album, title,
 track, name, genre, date, composer, performer, comment, disc,
 musicbrainz_artistid, musicbrainz_albumid, musicbrainz_albumartistid,
-musicbrainz_trackid.  Multiple tags may be specified as a comma separated list.
+musicbrainz_releasetrackid, musicbrainz_trackid.  Multiple tags may be specified
+as a comma separated list.
 An example value is "artist,album,title,track".  The special value "none" may
 be used alone to disable all metadata.  The default is to use all known tag
 types except for comments and those starting with "musicbrainz".

src/db/plugins/ProxyDatabasePlugin.cxx

@@ -166,6 +166,10 @@ static constexpr struct {
 	{ TAG_MUSICBRAINZ_ALBUMARTISTID,
 	  MPD_TAG_MUSICBRAINZ_ALBUMARTISTID },
 	{ TAG_MUSICBRAINZ_TRACKID, MPD_TAG_MUSICBRAINZ_TRACKID },
+#if LIBMPDCLIENT_CHECK_VERSION(2,10,0)
+	{ TAG_MUSICBRAINZ_RELEASETRACKID,
+	  MPD_TAG_MUSICBRAINZ_RELEASETRACKID },
+#endif
 	{ TAG_NUM_OF_ITEM_TYPES, MPD_TAG_COUNT }
 };
 

src/output/plugins/RoarOutputPlugin.cxx

@@ -349,6 +349,9 @@ roar_tag_convert(TagType type, bool *is_uuid)
 		case TAG_MUSICBRAINZ_TRACKID:
 			*is_uuid = true;
 			return "HASH";
+		case TAG_MUSICBRAINZ_RELEASETRACKID:
+			*is_uuid = true;
+			return "HASH";
 
 		default:
 			return nullptr;

src/tag/TagId3.cxx

@@ -259,6 +259,8 @@ tag_id3_parse_txxx_name(const char *name)
 		{ "MusicBrainz Album Artist Id",
 		  TAG_MUSICBRAINZ_ALBUMARTISTID },
 		{ "MusicBrainz Track Id", TAG_MUSICBRAINZ_TRACKID },
+		{ "MusicBrainz Release Track Id",
+		  TAG_MUSICBRAINZ_RELEASETRACKID },
 		{ nullptr, TAG_NUM_OF_ITEM_TYPES }
 	};
 

src/tag/TagNames.c

@@ -41,4 +41,5 @@ const char *const tag_item_names[TAG_NUM_OF_ITEM_TYPES] = {
 	[TAG_MUSICBRAINZ_ALBUMID] = "MUSICBRAINZ_ALBUMID",
 	[TAG_MUSICBRAINZ_ALBUMARTISTID] = "MUSICBRAINZ_ALBUMARTISTID",
 	[TAG_MUSICBRAINZ_TRACKID] = "MUSICBRAINZ_TRACKID",
+	[TAG_MUSICBRAINZ_RELEASETRACKID] = "MUSICBRAINZ_RELEASETRACKID",
 };

src/tag/TagType.h

@@ -54,6 +54,7 @@ enum TagType
 	TAG_MUSICBRAINZ_ALBUMID,
 	TAG_MUSICBRAINZ_ALBUMARTISTID,
 	TAG_MUSICBRAINZ_TRACKID,
+	TAG_MUSICBRAINZ_RELEASETRACKID,
 
 	TAG_NUM_OF_ITEM_TYPES
 };