> I haven't seen a practical example of a use case that's improved by having separate add and commit.

Well, I frequently see random things to fix while I'm working on a problem.

When I 'm ready to commit, I run `git status` and notice there's a file that's been modified that's unrelated to what I'm trying to commit.

A quick `git diff` later and I see what I did: fixed an unrelated issues. So I add that one file to the index, commit it with a relevant commit message, and then proceed to do a second commit—the one I had expected to do—also with a relevant commit message.

I do this 3-5 times a day, at least.