code: func (mp *MergePolicyImpl) isMerged(infos *SegmentInfos,
  	info *SegmentCommitInfo, w *IndexWriter) bool {
  	panic("not implemented yet")
  	assert(w != nil)
  	hasDeletions := w.readerPool.numDeletedDocs(info) > 0
  	return !hasDeletions &&
  		!info.Info.HasSeparateNorms() &&
  		info.Info.Dir == w.directory &&
  		(mp.noCFSRatio > 0 && mp.noCFSRatio < 1 || mp.maxCFSSegmentSize < math.MaxInt64)
  }
docs: /*
  Returns true if this single info is already fully merged (has no
  pending deletes, is in the same dir as the writer, and matches the
  current compound file setting)
  */