$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-pcoval2-10609-29163/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-pcoval2-10609-29163/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin 7071007323b0075e56fe4f03f06cb4fa21f35f02:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         7071007323b0075e56fe4f03f06cb4fa21f35f02 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7071007 bump release for test build