1235 notify third parties for changes in the license book

[barmac]

Closes #1235

[barmac]

Note for reviewer: We use diff package due to broken behaviour of Node's child_process module when diffing big different (edited) files.

[barmac]

@philippfromme ready.

[nikku]

We use diff package due to broken behaviour of Node's child_process module when diffing big files.

What is the broken behavior and why / how does it apply to setup?

[barmac]

Previously, I tried to use execa.sync to generate diff:

const exec = require('execa').sync;

const diff = exec('diff', ['-u', '-', file], { input: anotherFile }).stdout;

However, it always throws error when the files differ. diff simply exits with 1 for unidentical files and it's considered as error for child_process and execa 🙄. Cf. nodejs/node#19494 (comment).

Anyway, the alternative would be to read stdout from error which feels hacky for me. So instead of these guys we use npm package for diff.

[nikku]

Thanks for the note.

I'd personally prefer built-in utilities, especially if the alternative is to require another dependency that is really only required on the CI.

Just to understand correctly, what we'd need is something like this, right?

const exec = require('execa').sync;

async function computeDiff(file, otherFile) {

  // diff exits with <1> if a diff exists; we must account for that special behavior
  // cf. https://github.com/nodejs/node/issues/19494#issuecomment-374721063
  try {
    return exec('diff', ['-u', '-', file], { input: otherFile }).stdout;
  } catch (e) {

    if (e.code !== 1) {
      throw e;
    }
    
    return e.stdout;
  }
}

[philippfromme]

Should I review this or not?

[barmac]

@nikku Correct, this is more or less what I wrote before.

@philippfromme I'll include Nico's suggestion and then it's ready. Just a sec.

[barmac]

@philippfromme ready

[philippfromme]

🐎