stripmine

local enderchest = false
local torch = turtle.getItemCount(1)
local chests = turtle.getItemCount(2)
local dist = 0

function dump()
 if turtle.getItemCount(16)>0 then
  turtle.digDown()
  turtle.select(2)
  turtle.placeDown()
  for slot = 3,16,1 do
   turtle.select(slot)
   turtle.dropDown()
  end
  turtle.select(3)
  if enderchest then
   turtle.select(2)
   turtle.digDown()
  else
   chests = chests - 1
  end
 end
end

function digforw()
 if turtle.detect() then
  turtle.dig()
 end
 turtle.forward()
 dump()
 turtle.digUp()
 dump()
 dist = dist + 1
end

function home()
 turtle.turnLeft()
 turtle.turnLeft()
 if turtle.detectUp() then
  turtle.digUp()
 end
 turtle.up()
 for i=1,dist,1 do
  turtle.forward()
 end
 turtle.down()
 if torch==0 then
  print("Ran out of torches.")
 elseif chests==0 then
  print("Ran out of chests.")
 else
  print("Ran out of fuel.")
 end
 turtle.turnLeft()
 turtle.turnLeft()
end

function light()
 turtle.turnLeft()
 turtle.turnLeft()
 turtle.select(1)
 turtle.place()
 turtle.turnLeft()
 turtle.turnLeft()
 torch = torch - 1
end

local retdist = 0
local fuel = turtle.getFuelLevel()
function run()
 while (torch>0) and (chests>0) and (fuel>retdist) do
  for i=1,12,1 do
   digforw()
  end
  light()
  retdist = dist + 14
  fuel = turtle.getFuelLevel()
 end
 home()
end

run()