feat: last updated time in docs

[sbansal3096]

Motivation

Fixes #895

1. Find the last commit time of any doc
2. Used the npm cross-spawn library for the same.
3. Add a line at bottom of each doc showing last update time

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

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[endiliey]

Thanks for the PR.

Can you refactor the function to core/utils.js and optionally write a unit test for it ? Try to make it as general as possible

It can be something like

function getGitLastUpdated(filepath) {
  const timeStamp = parseInt(spawn.sync('git', ['log', '-1', '--format=%ct', filepath]).stdout.toString('utf-8')) * 1000;
  return new Date(timeStamp).toLocaleString();
}

Edit: In addition, what if Docusaurus user does not use Git ? We should omit the whole last updated and not display it at all (return null)

Another thing is that the docs are not just in website/versioned_docs. You should check the docs metadata and find that particular source of docs. (it could be in docs or website/translate_docs or website/versioned_docs.

For example, this current PR couldn't get the last update time of docs. (See the 'Invalid Date' below)

[sbansal3096]

@endiliey Thank you for your suggestions. Made the suggested changes. :)

[endiliey]

LGTM. Just few nits below before merging and would you mind to add test for getGitLastUpdated ? I think adding test is a very good practice. You can test at least 2 cases, valid file and invalid file

[endiliey]

Try Inline If with Logical && Operator which is more declarative

Example

{updateTime && <div>{updateTime}</div>}

[sbansal3096]

@endiliey Thanks for approving. Yes you are right, adding tests would be a great thing to do. But I had a few doubts regarding that.
Firstly, when testing should I compare the timestamp returned to some hard-coded timestamp or just that it's a string. Because the hard-coded timestamp would change if someone changes a doc.
Secondly, if git is not installed then these tests won't work right?

[endiliey]

You should use a test doc file (which we wont edit anymore) and put it in __fixtures__. The test could be a snapshot testing.

Then the second case is to test if there is no git timestamp, the function should return null. Similar to non existing file, return null

[JoelMarcey]

@sbansal3096 Excellent for your first PR to Docusaurus 👍

I am wondering if we should have a configuration option for this so folks can decide whether they want the last updated string?

[sbansal3096]

@JoelMarcey Sure! We can have that. By default should we keep it on or off?

[JoelMarcey]

We may have an issue with running npm start with this PR.

@sbansal3096 is investigating.

Edit by Endilie:
It is caused due to dependencies. Since we add a new npm package, we should add lockfile

[endiliey]

@sbansal3096
The test was failing so I patched your PR & rewrote the getGitLastUpdated test for you.

Just an extra suggestion, try creating new branch when creating a PR, do not send your forked master branch for PR

[endiliey]

@sbansal3096 mind to update the docs for https://docusaurus.io/docs/en/site-config.html#optional-fields for this changes ?

And resolve the conflict by merging master / you can rebase

[sbansal3096]

@endiliey Should I merge all the commits into 1 commit?

[endiliey]

No need @sbansal3096

I'll squash when merging it. LGTM. Are you ready to ship ?

[sbansal3096]

@endiliey Thanks alot. Yeah I am good to go. :)

[endiliey]

[JoelMarcey]

I approve these changes! 😄