requireNonNull(source, "source is null");
        requireNonNull(relativeTarget, "relativeTarget is null");
        if (Files.isRegularFile(source)) {
            throw new IllegalArgumentException("source file does not exist or is not a file");
        }
        if (relativeTarget.isAbsolute()) {
            throw new IllegalArgumentException("Supplied URI is not relative");
        }
        URI target = baseURI.resolve(relativeTarget);