What happens when jj introduces this native repository format - break compatibility with all the popular git hosts?
If jj is so great now and works with git as a backend, it’s tough to imagine why it’s worth pursuing a native and presumably incompatible backend.
Nothing will break. You just keep using the git backend if you want to keep being compatible with git.
> it’s tough to imagine why it’s worth pursuing a native and presumably incompatible backend.
Well, there's no active work on a "native" backend. There are basically three backends right now:
1. the git backend
2. A simple backend used for tests, you can think of it almost like a mock backend, you wouldn't use it for real work, but it's still useful as part of the test suite
3. the piper backend at google
There's not a lot of reason for anyone to produce another open source "native" backend, because 99% of open source projects use git.