I have _0.cfs file of a lucene index directory but segments.gen and segments_2 are missing. Can I generate the segments.gen and segments_2 files without having to regenerate the _0.cfs file. Does these "segments" files contain any index specific data, which will thus force me to regenerate the entire index again. Or can I just generate the two "segments" file by copying these from another lucene index directory generated with the same lucene version.