BuckarooBanzay

Despite all the comments saying to avoid submodules i can only recommend them.

I'm using them in several of my game servers as a "meta-repo" that points to other git repositories (for example here: https://github.com/pandorabox-io/pandorabox-mods)

It makes updating, finding/fixing bugs and testing much easier (we are using github's dependabot to update and kick off initial tests)

A far underrated engine/game in my opinion:

* Educational use: https://wiki.minetest.net/MinetestEDU

* Contributed mods: https://www.minetest.net/customize/

* Servers (all nonprofit): http://servers.minetest.net/

Would a simple backup/copy of the "charged" database have sufficed? e.g: backup the db with a 5$ charge, use the credits, restore the database...

For those interested in the educational part (as with minecraft) there is an article about using it in schools: https://wiki.minetest.net/MinetestEDU