$ git clone -n https://src.fedoraproject.org/rpms/R-Rmpfr.git /var/lib/mock/f45-build-5951-345/root/chroot_tmpdir/scmroot/R-Rmpfr
Cloning into '/var/lib/mock/f45-build-5951-345/root/chroot_tmpdir/scmroot/R-Rmpfr'...
$ git fetch origin d35953f70d14ebecabf992d0a3e03ea5a4d48e84:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-Rmpfr
 * [new ref]         d35953f70d14ebecabf992d0a3e03ea5a4d48e84 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d35953f Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild