What is the right way to have GitVersion report versioning from a different branch pointer?

[hotchkj]

I'm implementing some more advanced versioning reasoning in a build for pull requests. I want to know the version in the PR, and the version in the PR target branch.

Example: in Jenkins, I can have CHANGE_TARGET=master, while the actual code is checked out on the PR merge branch PR-1234. I'd like GitVersion to calculate version for the master HEAD as well as the PR-1234 HEAD.

What is the best/right way to do this? Are there missing features that would make this easier? I came across #3954 which suggests that I can't just temporarily override GIT_BRANCH.

I could probably just check out said branch and re-run GitVersion, but that's going to yield a lot of expensive churn in the repo. I am curious if there's a less brute-force approach.

Thanks for assistance!

[asbjornu]

We are discussing similar use of Git_Branch in #4212 (comment). I believe that if implemented, it would cover your use-case as well.