Function comment 

pub fn comment(
    path: &Path,
    feature: Option<&str>,
    op: CommentOp,
    anchor: Option<&CommentAnchor>,
    id: Option<&str>,
    text: Option<&str>,
    via: Via,
    state: Option<&Path>,
) -> CommandResult

Adds, deletes or keeps a comment (or keeps a revision turn, id tN), on the person’s command.