Introduce utility function for deriving table fields

tools/electric_drill.lua

@@ -15,8 +15,7 @@
 -- along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 local S=minetest.get_translator("industrialtest")
-industrialtest.ElectricDrillBase=table.copy(industrialtest.ActivatedElectricTool)
-industrialtest.internal.unpackTableInto(industrialtest.ElectricDrillBase,{
+industrialtest.ElectricDrillBase=industrialtest.internal.derive(industrialtest.ActivatedElectricTool,{
 	digs={
 		"cracky",
 		"crumbly"
@@ -33,8 +32,7 @@ function industrialtest.ElectricDrillBase.getOpPower(self,itemstack)
 	return 50
 end
 
-industrialtest.ElectricDrill=table.copy(industrialtest.ElectricDrillBase)
-industrialtest.internal.unpackTableInto(industrialtest.ElectricDrill,{
+industrialtest.ElectricDrill=industrialtest.internal.derive(industrialtest.ElectricDrillBase,{
 	name="industrialtest:electric_drill",
 	description=S("Electric Drill"),
 	inventoryImage="industrialtest_electric_drill.png",
@@ -60,8 +58,7 @@ minetest.register_craft({
 	}
 })
 
-industrialtest.AdvancedElectricDrill=table.copy(industrialtest.ElectricDrillBase)
-industrialtest.internal.unpackTableInto(industrialtest.AdvancedElectricDrill,{
+industrialtest.AdvancedElectricDrill=industrialtest.internal.derive(industrialtest.ElectricDrillBase,{
 	name="industrialtest:advanced_electric_drill",
 	description=S("Advanced Electric Drill"),
 	inventoryImage="industrialtest_advanced_electric_drill.png",