Thanks for your comments, Eli, I'm attaching an updated patch below.

Eli Zaretskii <eliz@gnu.org> writes:

>> This adds a new command to EWW that copies an alternate link to the
>> currently visited page into the kill ring.  This is useful for
>> subscribing to website feeds, etc..
>                                    ^^
> Two periods, one of which is probably redunant.
>

Fixed.

>> +@findex eww-copy-alternate-url
>> +@kindex A
>> +  The @kbd{A} command (@code{eww-copy-alternate-url}) copies the URL
>> +of an alternate link of the current page (such as an associated RSS
>> +feed) into the kill ring.  If the page specifies multiple alternate
>> +links, this command prompt for one of them in the minibuffer.
>
> This doesn't say anything about what an "alternate link" could be, it
> just provides a single example.  Since this is for the manual (as
> opposed to the doc string), there's no need to be so terse; we should
> instead explain more about what these alternate links are or could be,
> and give more than just a single example.  Perhaps also tell how the
> alternate links are designated in HTML.
>

Alright, I wasn't sure how much to elaborate here, I've added more
details in the updated patch.  I hope I got the formatting right for
referring to HTML elements, basically I tried to follow similar existing
cases in eww.texi.

>> +*** New command 'eww-copy-alternate-url'.
>> +It copies an alternate link to the page currently visited in EWW into
>> +the kill ring.
>
> Searching the Internet for "alternate link" brings this:
>
>   A type of hyperlink that gives alternate representations of the
>   current document.
>
> Is this what is meant here?  If so, why are you talking about RSS
> feeds?
>

Yes, websites very often use these alternate links to point to their
RSS/Atom feeds.  Should I add a couple of words about that in the NEWS
entry as well?

For instance, https://www.gnu.org/ lists
https://planet.gnu.org/rss20.xml as an alternate link (as well as
translations of that webpage to other languages).

There's more information about alternate links here
https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes/rel#alternate


>> +(defun eww-read-alternate-url ()
>> +  "Get the URL of an alternate link of this page.
>> +
>> +If there is just one alternate link, return it's URL.  If there
>                                                ^^^^
> "its"
>

Thanks, fixed.

>> +are multiple alternate links, prompt for one in the minibuffer.
>
> I guess the prompt is with completion?  If so, please mention that.
>

Done.

>> +(defun eww-copy-alternate-url ()
>> +  "Copy an alternate URL of the current page into the kill ring."
>
> This doc string says nothing at all about what an alternate link is.
> It should say at least something.
>

Sure, I've added a couple of words here as well.

>> +  (interactive nil eww-mode)
>> +  (if-let ((url (eww-read-alternate-url)))
>> +      (progn
>> +        (kill-new url)
>> +        (message "Copied %s to kill ring" url))
>> +    (user-error "No feeds found!")))
>
> "No feeds"?  Can the alternate link be something other than a feed?
> In any case, "No feeds found on this page!" is better, I think, as "No
> feeds!" is too general.

You're right, thanks, I've changed this to "No alternate links found on
this page!".