$ git clone -n https://src.fedoraproject.org/rpms/xen.git /var/lib/mock/f39-build-2553890-61951/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/f39-build-2553890-61951/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin ed0d7278e66e8f8cf81a0e01f185451fba9be2e6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xen
 * [new ref]         ed0d7278e66e8f8cf81a0e01f185451fba9be2e6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ed0d727 2 security updates