Replace Stream.readable.pipe() with data event API in getHash()

[seaoak]

What does it do?

Fix one of errors of the issue #3818. (#3818 (comment))

With Node.js v10.x, npm test fails some times.
One of them is process() - skip (mtime changed but hash matched): as follows:

  1) Hexo
       Box
         Box
           process() - skip (mtime changed but hash matched):
     AssertError: expected spy to be called with match
[_File] {
  params: {  },
  path: "a.txt",
  source: "J:\00_Seaoak\hexo\simplify_codeblock_escape\hexo\test\scripts\box\box_tmp\test\a.txt",
  type: "update"
} { path: "a.txt", type: "skip" }
      at Object.fail (J:\00_Seaoak\hexo\simplify_codeblock_escape\hexo\node_modules\sinon\lib\sinon\assert.js:107:21)
      at failAssertion (J:\00_Seaoak\hexo\simplify_codeblock_escape\hexo\node_modules\sinon\lib\sinon\assert.js:66:16)
      at Object.assert.(anonymous function) [as calledWithMatch] (J:\00_Seaoak\hexo\simplify_codeblock_escape\hexo\node_modules\sinon\lib\sinon\assert.js:92:13)
      at Context.it (J:\00_Seaoak\hexo\simplify_codeblock_escape\hexo\test\scripts\box\box.js:160:17)

This patch fixes this error.

I found that a combination Stream.readable.pipe() and Crypt.createHash() causes this error.
By replacing Stream.readable.pipe() with data event API, this error is resolved.

But I can not explain why this replacing does resolve this error.

How to test

nvm use 10.20.1
git clone -b workaround/fs.readable.pipe_not_work_well https://github.com/seaoak/hexo.git
cd hexo
npm install
npm test

Pull request tasks

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

[coveralls]

Coverage increased (+0.002%) to 97.743% when pulling 117e01f on seaoak:workaround/fs.readable.pipe_not_work_well into 714e752 on hexojs:master.

[segayuu]

Hash Stream Mode already uses Hash#digest() once when issuing the finish event. This behavior is correct when sending a hash value by connecting the stream with Hash#pipe(), but you cannot use Hash#digest() again in the 'finish' event.

[seaoak]

@segayuu Thank you for your information!

I understand the cause of errors, and make a new PR #4323 (replace this draft PR).