$ git clone -n https://src.fedoraproject.org/rpms/R-rversions.git /var/lib/mock/f38-build-side-42-init-devel-1392681-30946/root/chroot_tmpdir/scmroot/R-rversions
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1392681-30946/root/chroot_tmpdir/scmroot/R-rversions'...
$ git fetch origin af968f2333c6f193f8b8f4ac0eca15db4f76f0d0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-rversions
 * [new ref]         af968f2333c6f193f8b8f4ac0eca15db4f76f0d0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at af968f2 R-maint-sig mass rebuild