vTree

local tHeight = 8
local number = 22

local Height = 0

local function sel(item)
  for i=1,16 do
    if turtle.getItemCount(i) > 0 and turtle.getItemDetail(i).name == item then
      turtle.select(i)
      return true
    end
  end
  return false
end

function b()
  local a,c = turtle.inspect()
  if a then
    return c.name
  else
    return "minecraft:air"
  end
end

local function check()
  if Height % tHeight == 0 then
    if b() ~= "minecraft:dirt" then
      turtle.dig()
      sel("minecraft:dirt")
      turtle.place()
      turtle.select(1)
    end
  elseif Height % tHeight ==1 then
    if b() ~= "minecraft:sapling"  then
      turtle.dig()
      sel("minecraft:sapling")
      turtle.place()
      turtle.select(1)
    end
  else
    turtle.dig()
  end
end
turtle.select(1)
while Height < tHeight * number do
  check()
  repeat
    turtle.digUp()
  until turtle.up()
  Height = Height + 1
end
  check()
while Height > 0 do
  repeat
    turtle.digDown()
  until turtle.down()
  Height = Height - 1
  check()
end