$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-asultanov1-11509-29818/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-asultanov1-11509-29818/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin e26efcf7c76639efe4e890cbb5323fa1290eed70:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         e26efcf7c76639efe4e890cbb5323fa1290eed70 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e26efcf bump release for test build