fix(helpers, tag plugins): encode url by default

[curbengh]

What does it do?

Continuation of #3708, this PR deals with helpers and tag plugins.

How to test

git clone -b encode-url-helper https://github.com/curbengh/hexo.git
cd hexo
npm install
npm test

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

[curbengh]

Depending on use case, asset_path tag plugin might not need to encode url.

[coveralls]

Coverage decreased (-0.01%) to 97.237% when pulling 382b0de on curbengh:encode-url-helper into ffe4eaa on hexojs:master.

[curbengh]

url_for pending hexojs/hexo-util#82

[SukkaW]

Should we re-implement those helper using hexo-util?

For example:

// url_for.js
'use strict';

module.exports = function (path = '/', options) {
  const url_for = require('hexo-util').url_for.bind(this);
  return url_for(path, options)
};

[curbengh]

Should we re-implement those helper using hexo-util?

Definitely, once hexo-util v1.2.0 is published. To be refactored (in a separate PR):

• relative_url
• gravatar
• full_url_for

[curbengh]

Ready to review.

---

Just realized path is encoded twice if it's already encode (/foo/bar%20baz -> /foo/bar%25%20baz). Pending hexojs/hexo-util#92

[curbengh]

WIP, needs to utilize url_for() more.

Edit: refactored.

[curbengh]

Pending hexojs/hexo-util#92 & hexojs/hexo-util#94 to avoid encoding path twice.

[SukkaW]

I have no idea why the test on AppVeyor failed while the test on Travis CI successed.

[curbengh]

I have no idea why the test on AppVeyor failed while the test on Travis CI successed.

The test failure shows the actual is "/foo%5Cbar" where %5C is a backslash, so it's Windows path.

This PR replaces url.resolve('/', asset.path); with encodeURL('/' + asset.path), the removal of url.resolve() could be the cause. I'll try putting it back, in combination with encodeURL.

---

Seems to resolve it, now left double-encoding issue.
Pending hexojs/hexo-util#92 & hexojs/hexo-util#99

---

Looks like full_url_for() and url_for() currently don't support Windows path. Perhaps adding url.resolve() in those functions can help.

Edit: url.resolve() in full_url_for() wouldn't help

const { resolve } = require('url')
console.log(resolve('http://example.com/blog/', 'abc\hey\index.html'))
// http://example.com/blog/abcheyindex.html

Anyhow, Windows path may not be applicable for full_url_for() / url_for().

[curbengh]

html_tag of hexo-util needs to be updated for mail_to helper compatibility.

---

Located the issue:

const { parse } = require('url')
console.log(parse('mailto:abc@example.com'))
/*
Url {
  protocol: 'mailto:',
  slashes: null,
  auth: 'abc',
  host: 'example.com',
  port: null,
  hostname: 'example.com',
  hash: null,
  search: null,
  query: null,
  pathname: null,
  path: null,
  href: 'mail:abc@example.com'
}
*/

null path is appended, resulting in mailto:abc@example.comnull.

---

Fix created hexojs/hexo-util#102