Fix command preprocess cancelling and command changing

When a command with signed arguments is cancelled, message headers need to be sent out. Same thing for when the executed command is changed.

patches/server/0929-Fix-command-preprocess-cancelling-and-command-changi.patch

@@ -0,0 +1,40 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Nassim Jahnke <nassim@njahnke.dev>
+Date: Tue, 2 Aug 2022 19:16:23 +0200
+Subject: [PATCH] Fix command preprocess cancelling and command changing
+
+
+diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+index a68b737cdd1e9f1054e0fc3bfee92c20a062fab5..c39e6a96a120cd9c5f7734ead5dac2091fed7fc8 100644
+--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
++++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+@@ -2261,13 +2261,24 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
+         PlayerCommandPreprocessEvent event = new PlayerCommandPreprocessEvent(this.getCraftPlayer(), command, new LazyPlayerSet(this.server));
+         this.cserver.getPluginManager().callEvent(event);
+ 
+-        if (event.isCancelled()) {
+-            return;
+-        }
+         command = event.getMessage().substring(1);
+ 
+-        ParseResults<CommandSourceStack> parseresults = this.parseCommand(command);
+-        Map<String, PlayerChatMessage> map = (packet.command().equals(command)) ? this.collectSignedArguments(packet, PreviewableCommand.of(parseresults)) : Collections.emptyMap();
++        // Paper start - send message headers for cancelled or changed commands
++        ParseResults<CommandSourceStack> parseresults = this.parseCommand(packet.command());
++        Map<String, PlayerChatMessage> map = this.collectSignedArguments(packet, PreviewableCommand.of(parseresults));
++        if (event.isCancelled() || !packet.command().equals(command)) {
++            for (final PlayerChatMessage message : map.values()) {
++                player.server.getPlayerList().broadcastMessageHeader(message, Set.of());
++            }
++            if (event.isCancelled()) {
++                return;
++            }
++
++            // Remove signatures if the command was changed and use the changed command source stack
++            map.clear();
++            parseresults = this.parseCommand(command);
++        }
++        // Paper end
+         // CraftBukkit end
+         Iterator iterator = map.values().iterator();
+