fix spi blackwhole
implement IW.updatePendingMerges()
fix SPI design for MergePolicy
implement FlushByRamOrCountsPolicy.onInsert(0)
fix wrong underscore naming
implement TieredMergePolicy.findMerges()
implement DW.postUpdate()
implement DW.applyAllDeletes()
fix sync issue
fix codec name
fix IndexReader parent infer
fix size SPI in MergePolicy
change IndexSearcher to pointer form; enable searcher part in gl2.go; implement NewSearcher()
implement NewAssertingIndexSearcherFromContext(0)
implement PerFieldSimilarityWrapper.computeWeight()
implement RandomSimilarityProvider.Get(0)
fix NPE when cfs is false
implement CFW.close()
implement DirectCFSIndexOutput.close()
remove unused debug code