Is there a way to use JJ in existing repos managed by the Android Open Source Project repo tool? #9538

It seems the version of git I have (from Nix, likely this issue) is making all repositories with reftable format by default, which jj doesn't seem to support yet. repo was a red-herring, but I managed to get a non-colocated repo that should work:

git init --ref-format=files --bare <path/to/repo-backing.git>

git -C <path/to/repo-backing.git> remote add reftable-source file://<path/to/bare/repository/managed/by/repo.git>

git -C <path/to/repo-backing.git> fetch reftable-source '+refs/heads/*:refs/heads/*' 'refs/remotes/<name>/*:refs/remotes/<name>/*'

git -C <path/to/repo-backing.git> symbolic-ref HEAD refs/heads/master

git -C <path/to/repo-backing.git> remote add <name> ssh://<URI>

mkdir -p <non/colocated/repo/path>

jj git init --git-repo=<path/to/repo-backing.git>

jj bookmark track master --remote <name>

That worked. Since repo creates bare git repositories without a backing tree, it's possible to migrate the ref format with git refs migrate --ref-format=files since there are no worktrees in the bare repo. Doing that, and then running jj git init --colocate . and jj bookmark track master --remote <name> seems to have worked as well.

So #9358 combined with nixpkgs' version of git using reftable storage by default is the root cause.