"fds forget" feature proposal

Scenario: You accidentally git add’ed or dvc add’ed a path that you didn’t intend to.

It’s a commonly googled question: https://stackoverflow.com/questions/1274057/how-to-make-git-forget-about-a-file-that-was-tracked-but-is-now-in-gitignore

What fds forget can add:

1. Easier naming - no more googling required
2. Automatically detect whether the file is tracked by git or DVC
3. Remove the file from DVC cache if it is tracked by DVC (after confirmation from the user)
4. Remove the relevant .dvc file if it exists, and also make git forget about that file
5. More?

[guysmoilov]

Interesting potentially relevant project: https://rtyley.github.io/bfg-repo-cleaner/

[guysmoilov]

@indweller I think you also need to run some form of dvc gc after dvc remove. And sure, thank you!