Re: Documentation for car and cdr

[Richard M. Stallman]

    Violates the convention stated in `(elisp)Documentation Tips' that the
    first line of a docstring should not be wider than 67 characters.
    (71 in this case.)

That is unfortunate but could be solved like this:

       Return the car of cons cell (or list) CONS.  Given nil, return nil.


                        The only list that is not a cons cell is nil,
    which is mentioned on the same line.

The goal here is not to write the minimal logically correct statement.
The goal is to be helpful.