Enable regrowth of apples

Apples only regrow where they first appear on trees, either on mapgen or when grown from saplings (meaning apples that were placed by players won't regrow).
Once the tree is cut down in full (leaves removed), regrowth will stop.
New apples only grow in daylight, and take the same time as a sapling to grow.

mods/default/nodes.lua

@@ -737,6 +737,35 @@ minetest.register_node("default:apple", {
 	after_place_node = function(pos, placer, itemstack)
 		minetest.set_node(pos, {name = "default:apple", param2 = 1})
 	end,
+
+	after_dig_node = function(pos, oldnode, oldmetadata, digger)
+		if oldnode.param2 == 0 then
+			minetest.set_node(pos, {name = "default:apple_mark"})
+			minetest.get_node_timer(pos):start(math.random(300, 1500))
+		end
+	end,
+})
+
+minetest.register_node("default:apple_mark", {
+	description = "Apple Marker",
+	drawtype = "airlike",
+	paramtype = "light",
+	sunlight_propagates = true,
+	walkable = false,
+	pointable = false,
+	diggable = false,
+	buildable_to = true,
+	drop = "",
+	groups = {not_in_creative_inventory = 1},
+	on_timer = function(pos, elapsed)
+		if not minetest.find_node_near(pos, 1, "default:leaves") then
+			minetest.remove_node(pos)
+		elseif minetest.get_node_light(pos) < 11 then
+			minetest.get_node_timer(pos):start(200)
+		else
+			minetest.set_node(pos, {name = "default:apple"})
+		end
+	end
 })