doc: additional guidance about amending commits

[Farenheith]

In my first contribution, I got the amending guidance
wrongly and amended my commit to attend some requested
changes. So I added some more lines in the docs to help the
further contributors to don't make the same mistake that I did

[nodejs-github-bot]

Review requested:

• @nodejs/tsc

[aduh95]

I suggest instead we should remove this paragraph:

node/doc/guides/contributing/pull-requests.md

Lines 312 to 319 in e676942

	If you happen to make a mistake in any of your commits, do not worry. You can
	amend the last commit (for example if you want to change the commit log).
	```text
	$ git add any/changed/files
	$ git commit --amend
	$ git push --force-with-lease origin my-branch
	```

I think we don't want contributors to amend already-pushed commits in general, the only use case I can think of is if we want the commit message to change, but for most PRs that just doesn't happen (and if it does happen and the contributor doesn't know how to do it, a Node.js collaborator can do it for them). I'm thinking of something like https://github.com/nodejs/node/pull/41299/files#diff-b989d7ccc0bd9a756a048f0255df3bd9444a63f8cb667e4b7b2a9575da1800a0R307-R311. wdyt?

[Farenheith]

@aduh95 There's a pipeline that checks the first commit message, and when the PR has only one commit is easier to fix the commit message using amend, maybe the recommendation should be:

• To keep one commit before the PR
• To amend it in case of something wrong in the description. The fact that the pipeline that checks it fails fast helps with that.
• To add new commits for every fix after the PR is opened

[aduh95]

Note that if this check doesn't pass, it doesn't block the PR from landing. I don't think we should recommend folks from amending the commit; folks reading this guide are more likely to have checked the commit guidelines anyway, so chances are they won't need to amend their commit message. If the commit message is invalid and they notice the failed check once they open the PR, either they know already how to amend the commit message, either they don't, both are fine.

[Farenheith]

@aduh95 that seems fair. I'll update the PR removing this part

[aduh95]

LGTM. Do you want to amend the previous paragraph saying something like Force-pushing also complicates the review process, as it won't allow reviewers to get a quick glance on what have changed?

[Farenheith]

@aduh95 done

[aduh95]

Landed in 94c9f62