code: public static DefaultFileSet copy(FileSet source, BaseFolder target) throws IOException {
  		return copyInner(source, source.getManifestPath(), target);
  	}
docs: Creates a new file set at the specified location. All other properties
  are copied from this file set. Resources are copied to the new file set
  to the extent possible, see {@link #internalizeAllCopy()}.
  @param source the original file set
  @param target the new location, this must point to an existing directory. It is recommended,
  although not strictly required, that the folder is also empty.
  @return the created file set
  @throws IOException if an I/O error occurs