Don't create undo history item for a paste that does nothing.

Author: SuuperW

src/BizHawk.Client.Common/movie/tasproj/TasMovie.Editing.cs

@@ -237,15 +237,20 @@ public int CopyOverInput(int frame, IEnumerable<IController> inputStates)
 				Log[frame + i] = entry;
 			}
 
-			ChangeLog.EndBatch();
-			Changes = true;
 			if (firstChangedFrame != -1)
 			{
-				// TODO: Throw out the undo action if there are no changes.
+				ChangeLog.EndBatch();
+				Changes = true;
+
 				InvalidateAfter(firstChangedFrame);
+
+				ChangeLog.SetGeneralRedo();
+			}
+			else
+			{
+				ChangeLog.AbortBatch();
 			}
 
-			ChangeLog.SetGeneralRedo();
 			return firstChangedFrame;
 		}
 

src/BizHawk.Client.Common/movie/tasproj/TasMovie.History.cs

@@ -11,6 +11,7 @@ public interface IMovieChangeLog
 		bool IsRecording { get; set; }
 		void Clear(int upTo = -1);
 		bool BeginNewBatch(string name = "", bool keepOldBatch = false);
+		void AbortBatch();
 		void EndBatch();
 		int Undo();
 		int Redo();
@@ -146,6 +147,16 @@ public bool BeginNewBatch(string name = "", bool keepOldBatch = false)
 			return ret;
 		}
 
+		/// <summary>
+		/// Ends the current undo batch and deletes any undo actions it contains.
+		/// </summary>
+		public void AbortBatch()
+		{
+			_history.RemoveAt(_history.Count - 1);
+			Names.RemoveAt(Names.Count - 1);
+			UndoIndex--;
+		}
+
 		/// <summary>
 		/// Ends the current undo batch. Future changes will be one undo each.
 		/// If not already recording a batch, does nothing.
@@ -161,9 +172,7 @@ public void EndBatch()
 			var last = LatestBatch;
 			if (last.Count == 0) // Remove batch if it's empty.
 			{
-				_history.RemoveAt(_history.Count - 1);
-				Names.RemoveAt(Names.Count - 1);
-				UndoIndex--;
+				AbortBatch();
 			}
 			else
 			{