$ git clone -n https://src.fedoraproject.org/rpms/xen.git /var/lib/mock/f39-build-1572150-37783/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/f39-build-1572150-37783/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin ad078f957fcdc8755a8585f90368a012a6e8c530:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xen
 * [new ref]         ad078f957fcdc8755a8585f90368a012a6e8c530 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ad078f9 4 security issues