SPIGOT-4339: Add EntityTransformEvent

Thanks klugemonkey for some contributions in https://hub.spigotmc.org/stash/projects/SPIGOT/repos/bukkit/pull-requests/351/overview

By: nathat890 <nathat890@outlook.com>

paper-server/nms-patches/EntityMushroomCow.patch

@@ -1,14 +1,19 @@
 --- a/net/minecraft/server/EntityMushroomCow.java
 +++ b/net/minecraft/server/EntityMushroomCow.java
-@@ -1,6 +1,7 @@
- package net.minecraft.server;
+@@ -2,6 +2,12 @@
  
  import javax.annotation.Nullable;
-+import org.bukkit.event.player.PlayerShearEntityEvent; // CraftBukkit
  
++// CraftBukkit start
++import org.bukkit.craftbukkit.event.CraftEventFactory;
++import org.bukkit.event.entity.EntityTransformEvent;
++import org.bukkit.event.player.PlayerShearEntityEvent;
++// CraftBukkit end
++
  public class EntityMushroomCow extends EntityCow {
  
-@@ -23,6 +24,14 @@
+     public EntityMushroomCow(World world) {
+@@ -23,6 +29,14 @@
  
              return true;
          } else if (itemstack.getItem() == Items.SHEARS && this.getAge() >= 0) {
@@ -23,3 +28,15 @@
              this.world.addParticle(Particles.u, this.locX, this.locY + (double) (this.length / 2.0F), this.locZ, 0.0D, 0.0D, 0.0D);
              if (!this.world.isClientSide) {
                  this.die();
+@@ -35,6 +49,11 @@
+                     entitycow.setCustomName(this.getCustomName());
+                 }
+ 
++                // CraftBukkit start
++                if (CraftEventFactory.callEntityTransformEvent(this, entitycow, EntityTransformEvent.TransformReason.SHEARED).isCancelled()) {
++                    return false;
++                }
++                // CraftBukkit end
+                 this.world.addEntity(entitycow);
+ 
+                 for (int i = 0; i < 5; ++i) {