Implement Item.isRepairable in Crafting and Grindstone. Closes #5917

src/main/java/net/minecraftforge/common/extensions/IForgeItem.java

@@ -114,7 +114,7 @@ public interface IForgeItem
      *
      * @return True if reparable
      */
-    boolean isRepairable();
+    boolean isRepairable(ItemStack stack);
 
     /**
     * Determines the amount of durability the mending enchantment

src/main/java/net/minecraftforge/common/extensions/IForgeItemStack.java

@@ -425,4 +425,14 @@ public interface IForgeItemStack extends ICapabilitySerializable<CompoundNBT>
             return !other.isEmpty() && getStack().getCount() == other.getCount() && getStack().getItem() == other.getItem() &&
             (limitTags ? getStack().areShareTagsEqual(other) : ItemStack.areItemStackTagsEqual(getStack(), other));
     }
+
+    /**
+     * Determines if a item is reparable, used by Repair recipes and Grindstone.
+     *
+     * @return True if reparable
+     */
+    default boolean isRepairable()
+    {
+        return getStack().getItem().isRepairable(getStack());
+    }
 }