$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-asultanov2-11612-29902/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-asultanov2-11612-29902/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin 10e3fa07df0fe5a7019960bd0c9afcedc53a1b05:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         10e3fa07df0fe5a7019960bd0c9afcedc53a1b05 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 10e3fa0 bump release for test build