bug#46627: [External] : bug#46627: [PATCH] Add new help command 'describe-command'

[Drew Adams <drew.adams@oracle.com>]

> AFAIR, Emacs never meant completion to be a means of discovery.
> The discovery was always meant to be through "apropos" commands.

Emacs never originally meant a lot of things that
were later expanded (or repurposed to some degree)
to advantage.

This is normal for many processes of change.

Exaptation:

 https://en.wikipedia.org/wiki/Exaptation

Spandrel:

 https://en.wikipedia.org/wiki/Spandrel_(biology)

> > So the idea is to combine searching for commands
> > with looking up their documentation.
> 
> I'm not sure this is a good idea, FWIW.  For starters, it is limited:
> if you spot a command whose name sounds relevant, you have no simple
> way getting details about it.  Unlike apropos commands, which do
> provide such ways.

"You have no such simple way" ... until you do.

Icicles (and I'm sure some other 3rd-party code
that enhances completion) can provide help on
individual completion candidates.

When completion candidates are things that have
doc strings, Icicles shows the first line of the doc
string for the "current" completion candidate in the
mode-line of the *Completions* window.  When you
cycle among some candidates, you see their help there.

And you can hit a key to see the complete doc string
for the current candidate (it's shown in *Help*).

You mention apropos commands.  They're great in part
because they allow keyword & regexp matching.  This
is also true for Icicles completion.  You can use
`M-x' with a regexp pattern as input, to see all
commands whose names match.  And thus, to also get
access to their doc.

And unlike apropos, you can quickly change the match
pattern.  And you don't need to scan a long list of
output when you're only interested in the doc of
this, that, or the other matching name.

It's not that this is _better_ than apropos.  It's
different.  Each has advantages, just as `occur'
and Isearch have different advantages.

Is the _purpose_ of `M-x' to invoke a command?
Sure - or not.  Because you can _also_ use it to
browse command doc (and in other ways, not
mentioned), you can, if you want, sometimes use it
just for that - not bothering to invoke any command.

"Emacs never meant..."  Emacs never intended...
Right.  But now it does - at least with some
3rd-party packages.