musikr.tag: handle slash positions in xiph

Resolves #965.

CHANGELOG.md

@@ -23,6 +23,7 @@
 - M3U playlist file name is now proposed if one cannot be found within the file
 - Duration is now parsed from certain files that previously could not be parsed
 - ID3v2 tags are now parsed from WAV files
+- NN/TT tracks/discs are now handled in Vorbis
 - Music library will is less likely to fail to respond to updates
 - Hidden audio files can now be loaded
 - Sorting songs by date now uses songs date first, before the earliest album date

musikr/src/main/java/org/oxycblt/musikr/tag/format/Vorbis.kt

@@ -48,7 +48,10 @@ internal fun String.parseSlashPositionField() =
  * @see transformPositionField
  */
 internal fun parseXiphPositionField(pos: String?, total: String?) =
-    transformPositionField(pos?.toIntOrNull(), total?.toIntOrNull())
+    pos?.let { posStr ->
+        posStr.toIntOrNull()?.let { transformPositionField(it, total?.toIntOrNull()) }
+            ?: posStr.parseSlashPositionField()
+    }
 
 /**
  * Transform a raw position + total field into a position a way that tolerates placeholder values.