$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-asultanov2-10826-29342/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-asultanov2-10826-29342/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin c68df89e49e825ab9ec62ae567d41d62b7bc4c21:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         c68df89e49e825ab9ec62ae567d41d62b7bc4c21 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c68df89 bump release for test build