[tor-dev] Unable to clone gitian-builder repository

I apologise if this doesn't belong in this list and for my inexperience. I am trying to clone the gitian-builder repository to test out the deterministic builds, but I'm running into an issue: "warning: remote HEAD refers to nonexistent ref, unable to checkout." It creates the gitian-builder directory and a .git directory within, but it is otherwise empty. The command being run is: "git clone https://git.torproject.org/builders/gitian-builder.git" Should I be running a different command?