$ git clone -n https://src.fedoraproject.org/rpms/R-cellranger.git /var/lib/mock/f45-build-6001-345/root/chroot_tmpdir/scmroot/R-cellranger
Cloning into '/var/lib/mock/f45-build-6001-345/root/chroot_tmpdir/scmroot/R-cellranger'...
$ git fetch origin f0cefbfbf5f503e28278feb05f02a8def505e19c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-cellranger
 * [new ref]         f0cefbfbf5f503e28278feb05f02a8def505e19c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f0cefbf Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild