$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-psafont2-9711-28427/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-psafont2-9711-28427/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin 383684590f2bae1b1dfc7902a826d8e6f08a3528:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         383684590f2bae1b1dfc7902a826d8e6f08a3528 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3836845 bump release for test build