$ git clone -n https://src.fedoraproject.org/rpms/R-git2r.git /var/lib/mock/f45-build-6137-346/root/chroot_tmpdir/scmroot/R-git2r
Cloning into '/var/lib/mock/f45-build-6137-346/root/chroot_tmpdir/scmroot/R-git2r'...
$ git fetch origin d4c1353f8e857d423f45b31c9c69ebeb870156ab:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-git2r
 * [new ref]         d4c1353f8e857d423f45b31c9c69ebeb870156ab -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d4c1353 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild