$ git clone -n https://src.fedoraproject.org/rpms/R-IRkernel.git /var/lib/mock/f38-build-side-42-init-devel-1065481-29775/root/chroot_tmpdir/scmroot/R-IRkernel
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1065481-29775/root/chroot_tmpdir/scmroot/R-IRkernel'...
$ git fetch origin 0b8d082b7063f0105b7c84e7b0b6dd5e66cccac3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-IRkernel
 * [new ref]         0b8d082b7063f0105b7c84e7b0b6dd5e66cccac3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0b8d082 update to 1.3.2