Status update 2020-07-11: I will be without Internet access for the foreseeable future, starting from 2020-07-12. Please understand that I will only reply to your messages whenever I manage to get back. That may be in a few weeks from now or longer. It all depends on whether I secure enough income amidst the ongoing crisis. Apologies in advance for whatever inconvenience.
In this short video I show how to fixup staged changes into a local commit. This is another approach to rewriting your git history before pushing to the remote repository.
Also make sure to check my directly-related video demo on how to interactively rebase git commits with Magit