berry.lua

turtle.up()
turtle.forward()
local rotateright = true
local function turn_around()
    if rotateright then
        turtle.turnRight()
        turtle.forward()
        if turtle.detect() then return 1 end
        turtle.turnRight()
    else
        turtle.turnLeft()
        if turtle.detect() then return 1 end
        turtle.forward()
        turtle.turnLeft()
    end
    rotateright = not rotateright
end
while true do
    local is,data = turtle.inspectDown()
    local justrotated = false
    if is and data.name == "minecraft:sweet_berry_bush" then
        if data.state.age>=2 then
            turtle.digDown()
            turtle.placeDown()
        end
    end
    if turtle.detect() then
        if turn_around() then break end
        justrotated = true
    elseif not is then
        turtle.back()
        if turn_around() then break end
        justrotated = true
    else
        turtle.forward()
    end
    if justrotated and not turtle.detectDown() then
        break
    end
end