treefarm.lua

saplingSlot = 1
bonemealSlot = 2

function chopTree()
    turtle.dig()
    turtle.forward()

    while turtle.digUp() do turtle.up() end

    while turtle.down() do end

    turtle.back()
end

function fillChest()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.select(3)
    turtle.drop()
    turtle.turnLeft()
    turtle.turnLeft()
end

function detectTree()
    _, block = turtle.inspect()
    return block['name'] == "minecraft:log"
end

function makeTree()
    repeat
        turtle.select(saplingSlot)
        turtle.place()
        turtle.select(bonemealSlot)
        turtle.place()
    until detectTree()
end

while true do
    makeTree()
    chopTree()
    fillChest()
end