$ git clone -n https://src.fedoraproject.org/rpms/prunerepo.git /var/lib/mock/f45-build-28974-634/root/chroot_tmpdir/scmroot/prunerepo
Cloning into '/var/lib/mock/f45-build-28974-634/root/chroot_tmpdir/scmroot/prunerepo'...
$ git fetch origin 4e077682811f93e84a460964cb8bd2e2d8f74035:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/prunerepo
 * [new ref]         4e077682811f93e84a460964cb8bd2e2d8f74035 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4e07768 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild