staircase-builder-up.lua

while true do
  turtle.dig()

  while turtle.getItemCount() == 0 do
    if turtle.getSelectedSlot() == 16 then
      break
    end

    turtle.select(turtle.getSelectedSlot() + 1)
  end

  if turtle.getSelectedSlot() == 16 then
    break
  end

  turtle.place()

  if not turtle.up() then
    break
  end

  if not turtle.forward() then
    break
  end
end