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

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
 };