Relative path

To make relative path caculate unambiguously, follow strictly two rules.

1. think the current path as a directory, no matter it ends with slash or not.
2. the provided path ends with a slash the final path will end with a slash, vise versa.

Explain

Think /one/two/ and /one/two as the same. Both are /one/two/.

.. will be /one

../ will be /one/

. will be /one/two

./ will be /one/two/

Example

if current path is /abc/.

<a
  href="#"
  ph-link="."
  >will be: /abc</a
>

<a
  href="#"
  ph-link="../xyz"
  >will be: /xyz</a
>

<a
  href="#"
  ph-link="../xyz/"
  >will be: /xyz/</a
>

it("should remove the last slash", () => {
  tutil.setpathname("/abc/"); // treat it as a directory
  const dataUrl = ".";
  const url = urlUtil.calUrl(dataUrl);
  expect(url).toBe("/abc");
});

it("should add the last slash", () => {
  tutil.setpathname("/abc"); // treat it as a directory
  const dataUrl = "./";
  const url = urlUtil.calUrl(dataUrl);
  expect(url).toBe("/abc/");
});