When testing out the awesome changes from T9657, I ran into a case that seems like it might be a bug, where Arcanist ends up on detached HEAD after landing instead of the local branch that was landed onto, if the local landing branch has a different name from the remote branch it's tracking:
1. Create a new local tracking branch with a different name from its remote branch, e.g. `git checkout -b slv --track origin/superlongversion`
2. Create a feature branch that tracks the local branch, e.g. `arc feature somefeature slv`
3. Make changes on the feature branch, get them reviewed, and then run `arc land`
At this point, Arcanist successfully lands the changes into the local `slv` branch and pushes them to the `superlongversion` branch on `origin`, which is great. However, when it's done, it ends up on detached HEAD, because it can't find a local branch called `superlongversion`.
It would be nice if Arcanist checked out the local branch it landed onto in this case, rather than looking for a local branch with the same name as the remote branch that it ultimately pushed the changes to.