Don't record an undo step when all the songs inserted into the playlist were vetoed. Thanks schizosfera.

src/core/song.cpp

@@ -1255,6 +1255,11 @@ bool Song::operator==(const Song& other) const {
          beginning_nanosec() == other.beginning_nanosec();
 }
 
+uint qHash(const Song& song) {
+  // Should compare the same fields as operator==
+  return qHash(song.url().toString()) ^ qHash(song.beginning_nanosec());
+}
+
 QImage Song::LoadEmbeddedArt(const QString& filename) {
   QImage ret;
   if (filename.isEmpty())

src/core/song.h

@@ -385,4 +385,6 @@ Q_DECLARE_METATYPE(Song);
 typedef QList<Song> SongList;
 Q_DECLARE_METATYPE(QList<Song>);
 
+uint qHash(const Song& song);
+
 #endif // SONG_H

src/playlist/playlist.cpp

@@ -833,10 +833,16 @@ void Playlist::InsertItems(const PlaylistItemList& itemsIn, int pos, bool play_n
     songs << item->Metadata();
   }
 
-  QList<Song> vetoed;
+  const int song_count = songs.length();
+  QSet<Song> vetoed;
   foreach(SongInsertVetoListener* listener, veto_listeners_) {
     foreach(const Song& song, listener->AboutToInsertSongs(GetAllSongs(), songs)) {
-      vetoed.append(song);
+      // avoid veto-ing a song multiple times
+      vetoed.insert(song);
+    }
+    if (vetoed.count() == song_count) {
+      // all songs were vetoed and there's nothing more to do (there's no need for an undo step)
+      return;
     }
   }
 
@@ -847,7 +853,7 @@ void Playlist::InsertItems(const PlaylistItemList& itemsIn, int pos, bool play_n
       const Song& current = item->Metadata();
 
       if(vetoed.contains(current)) {
-        vetoed.removeOne(current);
+        vetoed.remove(current);
         it.remove();
       }
     }