git: export git ref to parent branch when possible

[jakobhellermann]

This is helpful for

• editors with git integration that show a warning when on an detached head (intellij etc.)
• using git and jj together on a repository

It is only done if there is a single parent with a single bookmark, otherwise it wouldn't be obvious which one to pick.

Checklist

• [ ] I have updated CHANGELOG.md
• [ ] I have added/updated tests to cover my changes

[martinvonz]

Another option is to always create/update a jj-specific branch. We could call it something like jj-<workspace id> (since there can be multiple workspaces).

[AngelEzquerra]

Another option is to always create/update a jj-specific branch. We could call it something like jj-<workspace id> (since there can be multiple workspaces).

I think this wojks be nice. It has the advantage that it can work even if you don’t use bookmarks.

[AngelEzquerra]

Another option is to always create/update a jj-specific branch. We could call it something like jj-<workspace id> (since there can be multiple workspaces).

FWIW I’ve been trying this approach manually ha today (by doing git branch --force jj-default followed by git switch jj-default after every jj new operation) and it works really well.