$ git clone -n https://src.fedoraproject.org/rpms/rust2rpm-helper.git /var/lib/mock/f40-build-799868-142612/root/chroot_tmpdir/scmroot/rust2rpm-helper
Cloning into '/var/lib/mock/f40-build-799868-142612/root/chroot_tmpdir/scmroot/rust2rpm-helper'...
$ git fetch origin a05b0d33580e21e36842388a17943b4d9902fc84:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust2rpm-helper
 * [new ref]         a05b0d33580e21e36842388a17943b4d9902fc84 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a05b0d3 Update to version 0.1.5; Fixes RHBZ#2265159