Alternative: I do a lot of commits just marked "wip" as I go, then when I'm ready to consider a PR, I rebase my branch into something for public consumption. Some commits will get thoughtful messages when warranted, others will get one line, and the PR description will tie it all together with screenshots and links to the most interesting parts.

(On a good day, that is. Though even on a bad day I don't let "wip" commits into the main branch.)