jodd-core/src/main/java/jodd/io/FileNameUtil.java
public static String relativePath(final String targetPath, final String basePath) {
		return new File(basePath).toPath().relativize(new File(targetPath).toPath()).toString();
	}
public static String relativePath(final String targetPath, final String basePath) {
		return new File(basePath).toPath().relativize(new File(targetPath).toPath()).toString();
	}
Calculates relative path of target path on base path.