It's my DarkMultiPlayer Savegame: contains a universe and craft, allows for easy syncing over the internet, and more importantly allows for revision tracking! Note that Git merge does not work on craft files; each part references the parent part's ID, and the tree as a whole is very hard to inject new parts into.
Observe the content of Update and Launch.command
to see what little in the way of "inner workings" this has.