text: public IndexAndTaxonomyRevision(IndexWriter indexWriter, SnapshotDirectoryTaxonomyWriter taxonomyWriter){this.indexSdp = indexWriter.Config.IndexDeletionPolicy as SnapshotDeletionPolicy;if (indexSdp == null)throw new ArgumentException("IndexWriter must be created with SnapshotDeletionPolicy", "indexWriter");this.indexWriter = indexWriter;this.taxonomyWriter = taxonomyWriter;this.taxonomySdp = taxonomyWriter.DeletionPolicy;this.indexCommit = indexSdp.Snapshot();this.taxonomyCommit = taxonomySdp.Snapshot();this.version = RevisionVersion(indexCommit, taxonomyCommit);this.sourceFiles = RevisionFiles(indexCommit, taxonomyCommit);}