Adds hard-delete for a beatmap diff

osu.Game/Beatmaps/BeatmapManager.cs

@@ -358,6 +358,31 @@ namespace osu.Game.Beatmaps
             });
         }
 
+        /// <summary>
+        /// Hard-Delete a beatmap difficulty locally.
+        /// </summary>
+        /// <remarks><see cref="Hide"/> is generally preferred as it keeps the local beatmap set in sync with the server.</remarks>
+        /// <param name="beatmapInfo">The beatmap difficulty to hide.</param>
+        public void DeleteLocal(BeatmapInfo beatmapInfo)
+        {
+            Realm.Run(r =>
+            {
+                using (var transaction = r.BeginWrite())
+                {
+                    if (!beatmapInfo.IsManaged)
+                        beatmapInfo = r.Find<BeatmapInfo>(beatmapInfo.ID);
+
+                    var setInfo = beatmapInfo.BeatmapSet!;
+                    DeleteFile(setInfo, beatmapInfo.File!);
+                    setInfo.Beatmaps.Remove(beatmapInfo);
+
+                    var liveSetInfo = r.Find<BeatmapSetInfo>(setInfo.ID);
+                    setInfo.CopyChangesToRealm(liveSetInfo);
+                    transaction.Commit();
+                }
+            });
+        }
+
         /// <summary>
         /// Delete videos from a list of beatmaps.
         /// This will post notifications tracking progress.

osu.Game/Screens/Edit/Editor.cs

@@ -851,7 +851,16 @@ namespace osu.Game.Screens.Edit
 
         private void deleteDifficulty()
         {
-            dialogOverlay?.Push(new PromptForDifficultyDeleteDialog(confirmDifficultyDelete, () => { }));
+            dialogOverlay?.Push(new PromptForDifficultyDeleteDialog(confirmDifficultyHide, confirmDifficultyDelete, () => { }));
+        }
+
+        private void confirmDifficultyHide()
+        {
+            var current = playableBeatmap.BeatmapInfo;
+            if (current is null) return;
+
+            beatmapManager.Hide(current);
+            switchBeatmapOrExit(current.BeatmapSet);
         }
 
         private void confirmDifficultyDelete()
@@ -859,8 +868,19 @@ namespace osu.Game.Screens.Edit
             var current = playableBeatmap.BeatmapInfo;
             if (current is null) return;
 
-            beatmapManager.Hide(current);
+            beatmapManager.DeleteLocal(current);
-            this.Exit();
+            switchBeatmapOrExit(current.BeatmapSet);
+        }
+
+        private void switchBeatmapOrExit([CanBeNull] BeatmapSetInfo setInfo)
+        {
+            if (setInfo is null || setInfo.Beatmaps.Count() <= 1)
+                this.Exit();
+            var nextBeatmap = setInfo!.Beatmaps.First();
+
+            // Force a refresh of the beatmap (and beatmap set) so the `Change difficulty` list is also updated.
+            Beatmap.Value = beatmapManager.GetWorkingBeatmap(nextBeatmap, true);
+            SwitchToDifficulty(Beatmap.Value.BeatmapInfo);
         }
 
         private void updateLastSavedHash()

osu.Game/Screens/Edit/PromptForDifficultyDeleteDialog.cs

@@ -9,7 +9,7 @@ namespace osu.Game.Screens.Edit
 {
     public class PromptForDifficultyDeleteDialog : PopupDialog
     {
-        public PromptForDifficultyDeleteDialog(Action delete, Action cancel)
+        public PromptForDifficultyDeleteDialog(Action hide, Action delete, Action cancel)
         {
             HeaderText = "Are you sure you want to delete this difficulty?";
 
@@ -17,9 +17,14 @@ namespace osu.Game.Screens.Edit
 
             Buttons = new PopupDialogButton[]
             {
+                new PopupDialogOkButton
+                {
+                    Text = @"Hide this difficulty instead (recommended)",
+                    Action = hide
+                },
                 new PopupDialogDangerousButton
                 {
-                    Text = @"Yes, delete this difficulty!",
+                    Text = @"Yes, DELETE this difficulty!",
                     Action = delete
                 },
                 new PopupDialogCancelButton