$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo /var/lib/mock/v8.3-incoming-10696-29244/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-incoming-10696-29244/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin 3187e6f112a591775077a8a94fc9d1e494b1c517:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         3187e6f112a591775077a8a94fc9d1e494b1c517 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3187e6f Merge pull request #13 from xcp-ng-rpms/pcoval/review/master