code: private void move(Resource ext) throws PageException {
  	Resource trg;
  	Resource trgDir;
  	try {
  	    trg = getExtensionFile(config, ext, id, name, version);
  	    trgDir = trg.getParentResource();
  	    trgDir.mkdirs();
  	    if (!ext.getParentResource().equals(trgDir)) {
  		if (trg.exists()) trg.delete();
  		ResourceUtil.moveTo(ext, trg, true);
  		this.extensionFile = trg;
  	    }
  	}
  	catch (Exception e) {
  	    throw Caster.toPageException(e);
  	}
      }
docs: copy the file to extension dir if it is not already there