public static boolean fileReferenceExistsOnDisk(File downloadDirectory, FileReference applicationPackageReference) {
        return getFileReferencesOnDisk(downloadDirectory).contains(applicationPackageReference.value());
    }
Returns all files in the given directory, non-recursive.
configserver/src/main/java/com/yahoo/vespa/config/server/filedistribution/FileDistributionUtil.java