$ git clone -n https://src.fedoraproject.org/rpms/R-errors.git /var/lib/mock/f40-build-2155871-50918/root/chroot_tmpdir/scmroot/R-errors
Cloning into '/var/lib/mock/f40-build-2155871-50918/root/chroot_tmpdir/scmroot/R-errors'...
$ git fetch origin 3eabfad40f37402e066b7eb844f2491b83d594d6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-errors
 * [new ref]         3eabfad40f37402e066b7eb844f2491b83d594d6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3eabfad Update to 0.4.1