You can clone with
HTTPS or Subversion.
It should at least be optional and default to user can interact, that's the whole point of GCD , preventing blocking of the UI.
It leaves the option of never blocking the UI and leaving that open for the developer to handle this in the view itself or passing as a parameter. I personally prefer just not blocking the UI and if the developer wants/needs that particular view to be blocked, he can do it directly.