I have forked a repo and branched that clone to code a story, and because I didn't understand the problem, wrote code that isn't solving my task at hand, but may prove useful later.
- Delete it, and don't worry about it. Then commit without the extra code.
- Make yet another branch for just that work, commit it, but don't post a pull request on it.
- Just commit it with the existing code, and worry about the extra "fluff" later.
I was thinking #2. If I understand correctly, I could just keep the extra code on a branch I never use on my clone, and dig it up later if something comes up that may benefit from using it.