bug#45333: complex command history should not save optional nil parameters

[Drew Adams]

> > (advice-add 'test :around (defun test-ad (f &rest args) args))
> > #+end_src
> >
> > the signature of `test' is still `(test &optional X)` as reported by
> C-h
> > f although the function is able to distinguish a specified nil from a
> > not specified optional argument.
> 
> `C-h f' lies, of course.  :-)  That is, `help-function-arglist'.
> (Which reminds me -- I've always found it odd that that function lives in
> help.el, and is in Emacs Lisp instead of C.  It is, after all, used by
> eldoc etc, and it'd probably be nice if it were more efficient.)

Please don't move it to C.
___

Advice isn't supported very well by Help (or vice versa).
(Perhaps "integrated with" instead of "supported by".)

The old advice system used to let you add to or replace
the doc-string text directly, so you saw it directly in
`*Help*'.  The new advice system tells you the function
is advised and gives you a link to the doc provided by
the advice.
___

And yeah, the Lisp calling sequence / signature is also
not supported/integrated.