If a PR is left open, then any further commits to the same branch automatically get added to the PR. So generally it is good to create PRs using feature branches, so you can control the effect and continue to work on other things. You do need to be careful of snowballing PRs - if the PR is constantly having new bits added, then those may have issues that need fixed causing there to be more time to add more bits to the PR.

I closed this one outright because I don't feel code related questions belong in the code itself - not sure what the best way to handle them is though.