$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-asultanov2-9462-28204/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-asultanov2-9462-28204/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin d581acffed0f0d0e654631b9cb5e821ec9e9cdc4:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         d581acffed0f0d0e654631b9cb5e821ec9e9cdc4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d581acf bump release for test build