bug#65027: 30.0.50; [PATCH] Document .elpaignore behavior in the Emacs Lisp manual

[Jim Porter]

On 8/3/2023 3:41 PM, Stefan Monnier via Bug reports for GNU Emacs, the 
Swiss army knife of text editors wrote:
> Historically, the difference was between the format of the repository
> (which only affected things like Melpa and (Non)GNU ELPA) and the format
> of ELPA tarballs (which is what `package.el` dealt with).
>
> `package-vc` makes the repository format relevant to `package.el`.
> But there might still be differences between what `package-vc` requires
> and what (Non)GNU ELPA requires, beside the data actually maintained in
> the (Non)GNU ELPA `elpa-packages`.

Yeah. I do think as a package author who once wasn't sure about exactly 
what I should do to make my Emacs package follow best-practices, the 
first place I'd look is in the Package section of the Emacs Lisp manual 
(regardless of where the implementations for package management live). 
But, like you say, now that 'package-vc' exists, Emacs itself now knows 
(some) about the repo format, too.

In any case, if there are no objections in the next day or two, I'll 
merge my patch, and then look into whether there are any other things 
worth documenting. (For example, I'll try to turn my suggested 
documentation on package naming[1] into a patch.)

[1] https://lists.gnu.org/archive/html/emacs-devel/2023-05/msg00452.html