$ git clone -n https://src.fedoraproject.org/rpms/R-rversions.git /var/lib/mock/f45-build-6394-348/root/chroot_tmpdir/scmroot/R-rversions
Cloning into '/var/lib/mock/f45-build-6394-348/root/chroot_tmpdir/scmroot/R-rversions'...
$ git fetch origin 526274a84e7610d688bac152cbe74716dfbafaf7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-rversions
 * [new ref]         526274a84e7610d688bac152cbe74716dfbafaf7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 526274a Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild