Oh, the script is fine, but Cuberite wouldn't build on my RasPi, that's why it doesn't update. PR 3281 takes care of that.
https://github.com/cuberite/cuberite/pull/3281
(but right now it doesn't build on Travis, wtf?)
https://github.com/cuberite/cuberite/pull/3281
(but right now it doesn't build on Travis, wtf?)