pub fn undo(
dir: &Path,
id: &str,
root: &Path,
) -> Result<(Vec<PathBuf>, usize), String>Expand description
Puts the cards back as they were before id, then forgets it. A card
changed since (a sync, an edit) is set aside first, as <id>.<n>.vcf
beside the record. Files outside root (the address books) are never
written; a card whose address book is gone stays gone. Returns the files
written back or removed, and how many versions were set aside.