To use git effectively (and as intended) I make small atomic commits, while I do have longer sessions where I do change not only one thing. Thus, I make heavy use of git a
You could commit an empty file with that path before making your changes. If you've already written things there, move the file away, make a blank file, commit that, then add -p as normal and git commit --amend so you don't have an "Add blank file" commit.