int unit_merge(Unit *u, Unit *other) {
        UnitDependency d;

        assert(u);
        assert(other);
        assert(u->manager == other->manager);
        assert(u->type != _UNIT_TYPE_INVALID);

        other = unit_follow_merge(other);

        if (other == u)
                return 0;

        if (u->type != other->type)
                return -EINVAL;

        if (!u->instance != !other->instance)
                return -EINVAL;

        if (other->load_state != UNIT_STUB &&
            other->load_state != UNIT_NOT_FOUND)
                return -EEXIST;

        if (other->job)
                return -EEXIST;

        if (other->nop_job)
                return -EEXIST;

        if (!UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other)))
                return -EEXIST;

        /* Merge names */
        merge_names(u, other);

        /* Redirect all references */
        while (other->refs)
                unit_ref_set(other->refs, u);

        /* Merge dependencies */
        for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++)
                merge_dependencies(u, other, d);

        other->load_state = UNIT_MERGED;
        other->merged_into = u;

        /* If there is still some data attached to the other node, we
         * don't need it anymore, and can free it. */
        if (other->load_state != UNIT_STUB)
                if (UNIT_VTABLE(other)->done)
                        UNIT_VTABLE(other)->done(other);

        unit_add_to_dbus_queue(u);
        unit_add_to_cleanup_queue(other);

        return 0;
}
Unknown