private Optional<Path> normalizePathInCommandLineProperties(final String propertyName) {
        final List<Path> paths = normalizePathsInCommandLineProperties(propertyName, false);
        if (paths.size() > 1) {
            throw new IllegalStateException("Multiple paths returned for an unsplit path.");
        }

        if (paths.isEmpty()) {
            return Optional.empty();
        }
        return Optional.of(paths.get(0));
    }
Returns a normalized path in a specified Java system property "user.home" or "user.dir".

<p>Note that a path in a Java system property should be an absolute path.
embulk-core/src/main/java/org/embulk/cli/EmbulkSystemPropertiesBuilder.java