code: private String getTempDir() {
          return (!customDir)
              ? CouchbaseLite.getTmpDirectory(TEMP_DIR_NAME)
              : CouchbaseLite.getTmpDirectory(directory, TEMP_DIR_NAME);
      }
docs: Returns the temp directory. The default temp directory is APP_CACHE_DIR/Couchbase/tmp.
  If a custom database directory is set, the temp directory will be
  CUSTOM_DATABASE_DIR/Couchbase/tmp.