That sounds awesome. A bit like plan9 philosophy "everything is a file". I wonder whether one could implement something like this with fuse+git (gitfs doesnt allow this, cf https://gitfs.readthedocs.io/en/stable/mount_options/)

With a thin layer of tooling, you could probably build a zfs CVS very easily. There's zfs send and each version is available under .zfs so you could use the patch/diff tool to see different versions and restore to older versions.

Microsoft Visual SourceSafe worked like this, but badly.

That would be very easy to do with FUSE. I would be amazed if it hasn't been done.

I doubt it's really that useful though - it would be difficult to make the filesystem mutable, which means anything that puts caches or build files in the tree (which is most things) wouldn't work.

I did a very quick search. First result: https://github.com/csutorasa/git-fuse

Sounds like the “jj edit” command.