$ git clone -n https://src.fedoraproject.org/rpms/R-biglm.git /var/lib/mock/f45-build-5983-345/root/chroot_tmpdir/scmroot/R-biglm
Cloning into '/var/lib/mock/f45-build-5983-345/root/chroot_tmpdir/scmroot/R-biglm'...
$ git fetch origin 2887e016e215dc46e98a85d3711a2ec544da9e49:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-biglm
 * [new ref]         2887e016e215dc46e98a85d3711a2ec544da9e49 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2887e01 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild