When using git as the VCS, if I committed something on my local `onto` branch (master) and then switch to a review branch and run `arc land`. Both changes will be pushed to the remote.
When I looked at ArcanistLandWorkflow.php it looks like the only case we will set `$local_ahead_of_remote` is when `git pull --ff-only --no-stat` fails and it is a git/svn repo. Both conditions do not apply in this case.
More than that, using `git pull` assumes that the `onto` branch is setup to correctly track the remote `onto` branch which is not always the case.