Function apply_override_answer 

pub fn apply_override_answer(
    answer: OverrideAnswer,
    stale: &[StaleCopy],
    home: &Path,
    stamp: &str,
    declined_file: &Path,
) -> Result<String>

Carries out answer for stale: moves the copies to a backup folder under home (named by stamp), removes them, or records the “no” in declined_file. Returns what it did, for the user.