bug#50936: "(emacs) Help" does say how to find external packages

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Fri, 1 Oct 2021 13:48:57 +0200
> 
> In (info "(emacs) Help"), I read:
> 
>      If you are looking for a certain feature, but don’t know what it is
>   called or where to look, we recommend three methods.  First, try an
>   apropos command, then try searching the manual index, then look in the
>   FAQ and the package keywords.
>   [...]
>   ‘C-h p’
>        This displays the available Emacs packages based on keywords.
>        *Note Package Keywords::.
> 
> The problem with this is that packages from GNU ELPA and NonGNU ELPA
> aren't listed here, so the better place to look should actually be
> 'M-x list-packages'.  Because that's where you'll find important modes
> for programming languages, etc.

"Modes" and "features" are not the same.  The latter refers to
features built into Emacs, i.e. to bundled packages.  If that isn't
clear from the text, we could clarify that, although it should be
quite obvious that an Emacs manual talks about bundled features.

> I'm not sure if the recommendation should be changed, or simply
> amended to also mention M-x list-packages.

It's okay to also mention list-packages, but if so, the text should
explicitly say that it's for features and packages not included in
the core distribution.

More importantly, I think we should seriously consider whether such
text has its place in that section.  That section is supposed to be a
cookbook for quickly and efficiently find Emacs features, so it should
be limited to methods and commands that accurate, in the sense that
they don't present the user with long lists of potential hits.  By
contrast, list-packages shows a very long list of packages (more than
400 as of this writing), which can easily overwhelm the user.  Even
"C-h p" doesn't show such long lists (the longest has 50 items), and
it is already too long, which is why it's the last in the list of
recommended methods.

> Or perhaps finder should list packages that are not installed?

Wouldn't that make "C-h p" less efficient, for the reason pointed out
above?