$ git clone -n https://src.fedoraproject.org/rpms/root.git /var/lib/mock/f39-build-1571874-37780/root/chroot_tmpdir/scmroot/root
Cloning into '/var/lib/mock/f39-build-1571874-37780/root/chroot_tmpdir/scmroot/root'...
$ git fetch origin 85ea6724079b37ce93d6b05734d1d0bbd29f2590:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/root
 * [new ref]         85ea6724079b37ce93d6b05734d1d0bbd29f2590 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 85ea672 Update to 6.28.08