Fix lag caused by Forge vehicle resync patch

This patch previously set the player to the entity's position,
which is not always correct for entities that position the player
at an offset (e.g. boats with two entities). Move the player using
positionRider() instead

Original PR: MinecraftForge/MinecraftForge#5160

Author: embeddedt

forge/src/main/java/org/embeddedt/modernfix/forge/mixin/bugfix/forge_vehicle_packets/ServerGamePacketListenerImplMixin.java

@@ -0,0 +1,28 @@
+package org.embeddedt.modernfix.forge.mixin.bugfix.forge_vehicle_packets;
+
+import net.minecraft.network.protocol.game.ServerboundMoveVehiclePacket;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.network.ServerGamePacketListenerImpl;
+import net.minecraft.world.phys.Vec3;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+@Mixin(ServerGamePacketListenerImpl.class)
+public class ServerGamePacketListenerImplMixin {
+    @Shadow public ServerPlayer player;
+
+    @Redirect(method = "handleMoveVehicle", at = @At(value = "INVOKE", target = "Lnet/minecraft/server/level/ServerPlayer;absMoveTo(DDDFF)V"))
+    private void movePlayerUsingPositionRider(ServerPlayer player, double x, double y, double z, float yRot, float xRot, ServerboundMoveVehiclePacket packet) {
+        if(player == this.player) {
+            // use positionRider
+            Vec3 oldPos = this.player.position();
+            this.player.getRootVehicle().positionRider(this.player);
+            this.player.xo = oldPos.x;
+            this.player.yo = oldPos.y;
+            this.player.zo = oldPos.z;
+        } else
+            player.absMoveTo(x, y, z, yRot, xRot);
+    }
+}