You can make as many commits as you need on your feature branch. When you're done with the feature, you do `git pull --rebase origin master` (or whatever the main branch is) and squash your commits into one (or a few -- when it makes sense) using `git rebase -i`.
I know the workflow of rebasing a feature branch into one commit on master, but that doesn't sound like what Pyxl101 was talking about, regarding the use of "git commit --amend" and "git commit --fixup".