$ git clone -n https://src.fedoraproject.org/rpms/R-remotes.git /var/lib/mock/f45-build-6350-348/root/chroot_tmpdir/scmroot/R-remotes
Cloning into '/var/lib/mock/f45-build-6350-348/root/chroot_tmpdir/scmroot/R-remotes'...
$ git fetch origin b4e1f12ff10d298129b6238a6d13bbad0a26b062:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-remotes
 * [new ref]         b4e1f12ff10d298129b6238a6d13bbad0a26b062 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b4e1f12 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild