$ git clone -n https://src.fedoraproject.org/rpms/R-purrr.git /var/lib/mock/f38-build-side-42-init-devel-1065505-29775/root/chroot_tmpdir/scmroot/R-purrr
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1065505-29775/root/chroot_tmpdir/scmroot/R-purrr'...
$ git fetch origin f56429bc65c60c0e7a1ea8adc9370a9f692a4f54:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-purrr
 * [new ref]         f56429bc65c60c0e7a1ea8adc9370a9f692a4f54 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f56429b 1.0.1