blockgame/mods/bg_tree/node_log.lua

local modname = minetest.get_current_modname()

local function reg_log (name, def)
	def = def or {}

	def.description = def.description or "Log"

	local texture = def.texture or name
	def.tiles = blockgame.underride(def.tiles, {
		modname .. "_" .. texture .. "_top.png",
		modname .. "_" .. texture .. "_top.png",
		modname .. "_" .. texture .. ".png",
	})

	def.groups = blockgame.underride(def.groups, {
		woody = 1,
		supports_leaves = 1,
	})

	blockgame.register_node(modname .. ":" .. name, def)
end

reg_log("log", {
	groups = {
		supports_leaves = 0,
	},
})
reg_log("log_alive", {
	groups = {
		planty = 1,
	},
	texture = "log",
	drop = modname .. ":log",
})
reg_log("sapling", {
	groups = {
		planty = 1,
	},
	drop = modname .. ":log",
})