add material and formation attribute to the carpets

api.lua

@@ -37,6 +37,8 @@ function carpets.register(recipe, def)
 		node.tiles = {node.tiles[6]}
 	end
 	node.groups.leafdecay = nil
+	node.material = recipe
+	node.formation = "carpet"
 
 	if config:get_bool("FallingCarpet") and node.groups.falling_node == nil then
 		node.groups.falling_node = 1

init.lua

@@ -19,6 +19,11 @@ local function filter(name, def)
 		return false
 	end
 
+	-- no 3rd hand carpets
+	if def.material then
+		return false
+	end
+
 	-- not supported node types for carpets
 	if def.drawtype == "liquid"    or
 	   def.drawtype == "firelike"  or