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

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Fri, 19 Feb 2021 11:42:50 -0600
> Cc: 46627@debbugs.gnu.org, Lars Ingebrigtsen <larsi@gnus.org>
> 
> The way I add it in the documentation treats it as more basic than
> `C-h f'.  That is, the proposed text first describes how to find
> documentation for commands, and only then describes how to find
> documentation for any Lisp function.  It is the most reasonable way to
> do it here, I think; this is after all the "user" manual and not the
> "Elisp" manual.

Please remember this when we discuss use of functions in user-level
features, such as values for user options.

> +@item C-h x @var{command} @key{RET}
> +Display documentation on the command named @var{command}

It is better to avoid duplicating "command" here.  Like this:

   Display documentation on the named @var{command}.

It is advantageous to use this style whenever the thing in @var{..} is
a term that explains itself clearly enough, like here.

> +  @kbd{C-h x @var{command} @key{RET}} (@code{describe-command})
> +displays the documentation of the command @var{command}, in a
                                     ^^^^^^^^^^^^^^^^^^^^^
Likewise.

> +displays the documentation of @code{auto-fill-mode}.  This is how you
> +would get the documentation of a command that is not bound to any key
> +(one which you would normally run using @kbd{M-x}).  Since all
> +commands are Lisp functions, you can also find its documentation using
> +@code{describe-function}.

The last sentence is better moved to the description of describe-function.

> +  @kbd{C-h f @var{function} @key{RET}} (@code{describe-function})
> +displays the documentation of Lisp function @var{function}.  This
                                      ^^^^^^^^^^^^^^^^^^^^^^^
Duplication of "function" again.  (Yes, I know it was that way in the
original text.)

> +@code{make-vector} properly, type @kbd{C-h f make-vector
> +@key{RET}}.

When a long text in |@kbd (or any other Texinfo markup) is near a
line's end, it is better to wrap it in @w{..}, so that it won't be
broken in half by the end of line.

> +    (unless (and fn (symbolp fn))
> +      (user-error "You didn't specify a function symbol"))
> +    (unless (or (fboundp fn) (get fn 'function-documentation))
> +      (user-error "Symbol's function definition is void: %s" fn))

These messages say "function" regardless of whether the user typed
"C-h x" or "C-h f".  Is that optimal?

Thanks.