I think this title is wrong.

Firstly some clarification - this appears to just be about the persistence format for his dive log. It was XML, now it's git based with plain text.

As someone who had to manage a system which worked with plain text files structured in a filesystem for a number of years in the 1990s, this is done to death already.

You now end up with the following problems: locking, synchronising filesystem state with the program, inode usage, file handles to manage galore and concurrency. All sorts.

Basically this is a "look I've discovered maildir and stuffed it in a git repo".

Not saying there is a better solution but this isn't a magic bullet. It's just a different set of pain.

The impression I got was that he was going to store his data in a git object database and that the files would be virtual in there. It would be like the .git directory without the working files on disk. It's all just conjecture until his code his out.

Regardless, I would think that some applications are simple enough (store few enough separate objects in the file system) that the issues you cite are not likely to cause a problem.