$ git clone -n https://src.fedoraproject.org/rpms/gvisor-tap-vsock.git /var/lib/mock/f42-build-866724-174073/root/chroot_tmpdir/scmroot/gvisor-tap-vsock
Cloning into '/var/lib/mock/f42-build-866724-174073/root/chroot_tmpdir/scmroot/gvisor-tap-vsock'...
$ git fetch origin b109f93a585e03027e2a3ec6fac16f393a4d030c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gvisor-tap-vsock
 * [new ref]         b109f93a585e03027e2a3ec6fac16f393a4d030c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b109f93 Update to 0.8.1 upstream release