cdm/src/main/java/thredds/inventory/partition/DirectoryCollection.java
public static Path makeCollectionIndexPath(String topCollectionName, Path dir, String suffix) {
    String collectionName = makeCollectionName(topCollectionName, dir);
    return Paths.get(dir.toString(), collectionName + suffix);
  }
public static Path makeCollectionIndexPath(String topCollectionName, Path dir, String suffix) {
    String collectionName = makeCollectionName(topCollectionName, dir);
    return Paths.get(dir.toString(), collectionName + suffix);
  }
Create standard name = topCollectionName + last directory
@param topCollectionName from config, name of the collection
@param dir directory for this
@return  standard collection name, to name the index file