Comment by dllthomas

A PR should do one thing at a higher level than a commit should do one thing (both at a different level than a function should do one thing).

I expect we're agreed that most PRs should be a single commit with a small number of changes in a small number of places, but IME it's not rare to have situations where dividing the changes into groups makes things clearer but where elevating those groups to the level of PR would make things less clear.