Option to store branches in head refs

[schacon]

We're storing the virtual branch refs in the refs/gitbutler namespace so as to not pollute the normal git branch space, but I'm hearing a lot of feedback that they might be better stored in the normal refs/heads space as like gitbutler/branch-A instead. We could just move them there, or we could have a setting, I'm not sure which is better.

[schacon]

Now that I think about this, I remember another reason why we did this. I don't want people to check out the gitbutler branches directly and do work on them. If that happens, then we would need to scan the refs for virtual branches and make sure they align, otherwise it will act a bit strangely.

[schacon]

In that case, I suppose we could watch for updates to these refs and then just update both the tree and head entries in the associated virtual branch while we're in our "not on gitbutler/integration" state.