$ git clone -n https://src.fedoraproject.org/rpms/R-nanotime.git /var/lib/mock/f45-build-6293-347/root/chroot_tmpdir/scmroot/R-nanotime
Cloning into '/var/lib/mock/f45-build-6293-347/root/chroot_tmpdir/scmroot/R-nanotime'...
$ git fetch origin 3fa6e86e58ea14500e110f6efc8232a02185516e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-nanotime
 * [new ref]         3fa6e86e58ea14500e110f6efc8232a02185516e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3fa6e86 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild