$ git clone -n https://src.fedoraproject.org/rpms/xen.git /var/lib/mock/f38-build-side-42-init-devel-584174-26102/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-584174-26102/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin bf947f8f9369e91f4cc0a1f3bef036338e2eecd2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xen
 * [new ref]         bf947f8f9369e91f4cc0a1f3bef036338e2eecd2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bf947f8 3 security issues (#2180425)