$ git clone -n https://src.fedoraproject.org/rpms/xbg.git /var/lib/mock/f45-build-38614-726/root/chroot_tmpdir/scmroot/xbg
Cloning into '/var/lib/mock/f45-build-38614-726/root/chroot_tmpdir/scmroot/xbg'...
$ git fetch origin bf2ce45dd44c729409bb1e01004109bf4dac6d3a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xbg
 * [new ref]         bf2ce45dd44c729409bb1e01004109bf4dac6d3a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bf2ce45 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild