$ git clone -n https://src.fedoraproject.org/rpms/root.git /var/lib/mock/f40-build-797442-141349/root/chroot_tmpdir/scmroot/root
Cloning into '/var/lib/mock/f40-build-797442-141349/root/chroot_tmpdir/scmroot/root'...
$ git fetch origin c2cd7682c3bcdf161e4c7632f702f9112418c3b0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/root
 * [new ref]         c2cd7682c3bcdf161e4c7632f702f9112418c3b0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c2cd768 Update to 6.30.04