$ git clone -n https://src.fedoraproject.org/rpms/R-testthat.git /var/lib/mock/f38-build-side-42-init-devel-762378-27707/root/chroot_tmpdir/scmroot/R-testthat
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-762378-27707/root/chroot_tmpdir/scmroot/R-testthat'...
$ git fetch origin dd66ece86164b081ce616d2021adf539e8851fbd:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-testthat
 * [new ref]         dd66ece86164b081ce616d2021adf539e8851fbd -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dd66ece update to 3.1.6