add !mp removeref and !mp listrefs

osu.Game/Online/Chat/StandAloneChatDisplay.cs

@@ -711,12 +711,12 @@ private void postMessage(TextBox sender, bool newText)
                             userReq = new GetUserRequest(patchedUsername);
                             userReq.Success += u =>
                             {
-                                Logger.Log($@"[addref] Successfully resolved user ${u}");
+                                Logger.Log($@"[{nameof(StandAloneChatDisplay)}] Successfully resolved user ${u}");
                                 tcs.TrySetResult(u);
                             };
                             userReq.Failure += e =>
                             {
-                                Logger.Log($@"[addref] Could not resolve user {patchedUsername}");
+                                Logger.Log($@"[{nameof(StandAloneChatDisplay)}] Could not resolve user {patchedUsername}");
                                 tcs.TrySetResult(null);
                             };
 
@@ -725,25 +725,47 @@ private void postMessage(TextBox sender, bool newText)
                             return await tcs.Task.ConfigureAwait(false);
                         }
 
-                        // special-case addref. only handle it locally
-                        if (parts.Length == 3 && parts[1] == @"addref")
+                        void printRefsList() => EnqueueBotMessage($@"Match referees: {string.Join(", ", multiplayerRefereeTracker.Referees)}");
+
+                        switch (parts.Length)
                         {
-                            queryUsername(parts[2]).ContinueWith(t =>
-                            {
-                                APIUser? user = t.GetResultSafely();
+                            // special-case addref. only handle it locally
+                            case 3 when parts[1] == @"addref":
+                                queryUsername(parts[2]).ContinueWith(t =>
+                                {
+                                    APIUser? user = t.GetResultSafely();
+
+                                    if (user == null)
+                                    {
+                                        EnqueueBotMessage($@"Failed to find user {parts[2]}");
+                                        return;
+                                    }
+
+                                    multiplayerRefereeTracker.AddRef(user);
+                                    printRefsList();
+                                });
+                                break;
 
-                                if (user == null)
+                            case 3 when parts[1] == @"removeref":
+                            {
+                                if (parts[2].Length == 0 || !multiplayerRefereeTracker.RemoveRef(parts[2]))
                                 {
-                                    EnqueueBotMessage($@"Failed to find user {parts[2]}");
-                                    return;
+                                    EnqueueBotMessage($@"No referee found matching '{parts[2]}'");
+                                    break;
                                 }
 
-                                multiplayerRefereeTracker.AddRef(user);
-                                EnqueueBotMessage($@"Match referees: {string.Join(", ", multiplayerRefereeTracker.Referees)}");
-                            });
-                        }
+                                printRefsList();
+                                break;
+                            }
 
-                        processChatCommands(parts);
+                            case 2 when parts[1] == @"listrefs":
+                                printRefsList();
+                                break;
+
+                            default:
+                                processChatCommands(parts);
+                                break;
+                        }
                     }
                 }
             }

osu.Game/Screens/OnlinePlay/Multiplayer/MultiplayerMatchSubScreen.cs

@@ -86,12 +86,24 @@ private void load()
             client.RoomUpdated += onRoomUpdated;
         }
 
-        public void AddRef(APIUser user)
+        public bool AddRef(APIUser user)
         {
-            if (!Referees.Contains(user))
-            {
-                Referees.Add(user);
-            }
+            if (Referees.Contains(user))
+                return false;
+
+            Referees.Add(user);
+            return true;
+        }
+
+        public bool RemoveRef(string username)
+        {
+            var user = Referees.FirstOrDefault(u => u.Username == username);
+            return user != null && RemoveRef(user);
+        }
+
+        public bool RemoveRef(APIUser user)
+        {
+            return Referees.Remove(user);
         }
 
         private void onRoomUpdated()