$ git clone -n https://src.fedoraproject.org/rpms/rust2rpm-helper.git /var/lib/mock/f40-build-2122298-50742/root/chroot_tmpdir/scmroot/rust2rpm-helper
Cloning into '/var/lib/mock/f40-build-2122298-50742/root/chroot_tmpdir/scmroot/rust2rpm-helper'...
$ git fetch origin 7dce271b22e22d90c823cadabdeaf6f7d8f69e20:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust2rpm-helper
 * [new ref]         7dce271b22e22d90c823cadabdeaf6f7d8f69e20 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7dce271 Update to version 0.1.4; Fixes RHBZ#2252420