$ git clone -n https://src.fedoraproject.org/rpms/R-mockr.git /var/lib/mock/f38-build-side-42-init-devel-1087061-30039/root/chroot_tmpdir/scmroot/R-mockr
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1087061-30039/root/chroot_tmpdir/scmroot/R-mockr'...
$ git fetch origin 9405df940b8ec79ffb6586b0a5dfb4cdae8989b4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-mockr
 * [new ref]         9405df940b8ec79ffb6586b0a5dfb4cdae8989b4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9405df9 update to 0.2.1