public NodeList rebuilding(boolean soft) {
        return matching(node -> {
            if (soft) {
                return !node.status().wantToRetire() && node.status().wantToRebuild();
            }
            return node.status().wantToRetire() && node.status().wantToRebuild();
        });
    }
Returns the subset of nodes that are being rebuilt.

@param soft When true, return only hosts that are being rebuilt without retirement
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/NodeList.java