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

[Stefan Monnier]

> I think there's just two levels that are interesting.  We have the er
> advertised calling convention (whether from
> advertised-calling-convention or "(fn ...)"), and then the real, actual
> for sure arglist.

The "actual for sure arglist" is the one that sometimes comes with
bogus names.

> The actual for sure arglist is needed when you want to redefine
> functions and the like, and need to actually retain the interface in all
> details, and today you have to look at the source code to do that, which
> a self-documenting editor shouldn't need.  (But it's pretty rare to need
> this, so it doesn't matter that it's slow.)

In my experience once you get to places where you need to care about
"the actual for sure arglist" the real needs depend a lot on the
specifics, so it's not even clear what would be a good answer that works
across the board (e.g. in the presence of CL's &key arguments).
The answer you get from `help-function-arglist` without the
`preserve-names` arg should be good enough for most cases.

I do think the current situation kinda sucks because stashing arglists
inside docstrings is a PITA, but it does have its advantages and
I haven't seen a good alternative yet.


        Stefan