Work-around lack of album-artist in mtp

TODO

@@ -29,3 +29,11 @@
 - PlayQueue - slow with over 2000 entries, due to sort-filter-proxy??
 
 - icecast?
+
+- libMTP album artist usage.
+  - libMTP does not provide an album artist tag.
+  - song.cpp has a heck to see if this.albumartist=other.album artist, so that when
+    library is frefreshed the file is in the correct place.
+  - mtpdevice.cpp will remove albumartist from 'Song' entries copied to it, so that
+    these are placed in the correct part of the model.
+  - If libMPT is 'fixed' then the above can be rmeoved.

devices/mtpdevice.cpp

@@ -151,8 +151,8 @@ void MtpConnection::updateLibrary()
         }
         s.album=track->album;
         s.artist=track->artist;
-        s.albumartist=s.artist; // libMTP does not support album artist :-(
-        // Use LIBMTP_Get_File_To_File_Descriptor to pass to TagLib!!!
+        // TODO: ALBUMARTIST: Read from 'track' when libMTP supports album artist!
+        s.albumartist=s.artist;
         s.year=QString::fromUtf8(track->date).mid(0, 4).toUInt();
         s.title=track->title;
         s.genre=track->genre;
@@ -495,7 +495,9 @@ void MtpDevice::addSong(const Song &s, bool overwrite)
         return;
     }
     qWarning() << "EMIT PUT SONG";
-
+    currentSong=s;
+    // TODO: ALBUMARTIST: Remove when libMPT supports album artist!
+    currentSong.albumartist=currentSong.artist;
     emit putSong(s);
 }
 

mpd/song.cpp

@@ -66,7 +66,10 @@ Song & Song::operator=(const Song &s)
 
 bool Song::operator==(const Song &o) const
 {
-    return file == o.file;
+    // When transfferring off an MPT device we will not have AlbumArtist, as libMTP does not handle this.
+    // But, MPD does, so if the labum artist is different - then treat as a new file.
+    // TODO: ALBUMARTIST: This check can be removed when libMTP supports album artist.
+    return file == o.file && albumartist==o.albumartist;
 }
 
 bool Song::operator<(const Song &o) const