This.

I just learned this recently. Intuitively, I had assumed that I could .gitignore a file and have it not show up in `git status`, even after staging it with `git add -f` and committing it this way.

Turns out: That's not how it works. Instead, the .gitignore entries simply don't count for any already tracked files.

(Yes, I know about `git update-index --assume-unchanged` but that has its own set of drawbacks…)