Contribution guide: add guidance for when to add commits to a PR vs. amending/squashing

[akoeplinger]

It's often not clear how to react to code review feedback (e.g. see the discussion here), should you add a new commit or just amend the previous one?

I think it'd be good to have an "official" guidance on this in the contributing doc to prevent confusion.

@stephentoub's response looks like a good basis to me:

In this case I'd suggesting adding additional commits and then squashing later. Personally, I prefer to just ammend the existing commit when the changes are small / trivial and I don't expect anyone to need to re-review, e.g. fixing up typos or making simple one-line fixes. For larger things, I prefer to have the additional commits so that it's clear to a reviewer what's changed.

Thoughts?

[Maxwe11]

dup #14315

[akoeplinger]

Thanks, glad it's not just me 😄

Closing this, but it'd be great if @terrajobst or @richlander could take a look at #14315 and discuss how we should move forward.