FR: A revset to determine the main branch in a repository.

[PhilipMetzger]

Is your feature request related to a problem? Please describe.
Add a revset to determine the quasi main "branch" in a repository, similar to immutable_heads().

Describe the solution you'd like
Add some repo- and user setting to determine a main branch in a repository, as it will be useful for the jj native forge.
As it probably won't be as branching oriented as Git is.

Additional context
This was previously a hidden FR in #1431.

[PhilipMetzger]

Anothre issue which relates to this is #1415.

[thoughtpolice]

Isn't this just trunk()?

[PhilipMetzger]

No, trunk() is a approximation to work with Git :-), this one is independant of backend.

[yuja]

No, trunk() is a approximation to work with Git :-), this one is independant of backend.

In what way trunk() is Git specific? If there's a jj native repo, I expect trunk() will be resolved to the main branch in that context. If the branching model is quite different from ::<head-commit-of-the-main-branch>, trunk() wouldn't work, though.

[martinvonz]

I also don't understand what this FR is about. FWIW, we have overridden trunk at Google to count main@piper as our trunk (piper is the name of our internal, non-Git remote).

[PhilipMetzger]

I made some mistakes yesterday, as mentioned trunk() adresses this issue, so I'm closing it.