$ git clone -n https://src.fedoraproject.org/rpms/gnome-shell.git /var/lib/mock/f42-build-side-1-3585673-46906/root/chroot_tmpdir/scmroot/gnome-shell
Cloning into '/var/lib/mock/f42-build-side-1-3585673-46906/root/chroot_tmpdir/scmroot/gnome-shell'...
$ git fetch origin 446e20673dd62fd559562e808ad191fc8c81517d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-shell
 * [new ref]         446e20673dd62fd559562e808ad191fc8c81517d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 446e206 Update to 48.3