TreeChopper

height = 0

while true do
    chop()
end

function chop()
    turtle.dig()
    turtle.forward()
    turtle.digDown()
    while turtle.detectUp() == true do
        turtle.digUp()
        turtle.up()
        height = height + 1
    end
    while height > 0 do
        turtle.down()
        height = height - 1
    end
    goBack()
end

function goBack()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.forward()
    turtle.turnLeft()
    turtle.turnLeft()
end