Introduce utility function for deriving table fields

tools/batpack.lua

@@ -15,8 +15,7 @@
 -- along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 local S=minetest.get_translator("industrialtest")
-industrialtest.BatPackBase=table.copy(industrialtest.ElectricGearTool)
-industrialtest.internal.unpackTableInto(industrialtest.BatPackBase,{
+industrialtest.BatPackBase=industrialtest.internal.derive(industrialtest.ElectricGearTool,{
 	part="torso"
 })
 
@@ -41,8 +40,7 @@ function industrialtest.BatPackBase.update(self,player,inv,itemstack,dtime)
 	return false
 end
 
-industrialtest.BatPack=table.copy(industrialtest.BatPackBase)
-industrialtest.internal.unpackTableInto(industrialtest.BatPack,{
+industrialtest.BatPack=industrialtest.internal.derive(industrialtest.BatPackBase,{
 	name="industrialtest:batpack_v",
 	description=S("BatPack"),
 	inventoryImage="industrialtest_batpack_v_inv.png",
@@ -63,8 +61,7 @@ minetest.register_craft({
 	}
 })
 
-industrialtest.LapPack=table.copy(industrialtest.BatPackBase)
-industrialtest.internal.unpackTableInto(industrialtest.LapPack,{
+industrialtest.LapPack=industrialtest.internal.derive(industrialtest.BatPackBase,{
 	name="industrialtest:lappack_v",
 	description=S("LapPack"),
 	inventoryImage="industrialtest_lappack_v_inv.png",