bug#40280: gnus-cloud doesn't do anything useful

[Basil L. Contovounesios]

> From a3bdd2219855a72e2ee90de1b6f823c9678a470c Mon Sep 17 00:00:00 2001
> From: David Edmondson <dme@dme.org>
> Date: Sat, 28 Mar 2020 19:03:58 +0000
> Subject: [PATCH] gnus-cloud: Improve cloud sync
>
> After replaying a set of actions downloaded by gnus-cloud, persist the
> highest sequence number seen as the local `gnus-cloud-sequence'
> number, in order that a future download will not unnecessarily replay
> previously seen actions and any future uploads from this emacs
> instance use a higher sequence number than that downloaded.
>
> Remove the test on whether individual newsrc entries are older than
> the current time, as that is always going to be the case.

In the future please follow the formatting guidelines for change log
messages described in the file CONTRIBUTE.

[...]

> --- a/lisp/gnus/gnus-cloud.el
> +++ b/lisp/gnus/gnus-cloud.el
> @@ -480,7 +478,9 @@ Otherwise, returns the Gnus Cloud data chunks."
>            (push (gnus-cloud-parse-chunk) chunks)
>            (forward-line 1))))
>      (if update
> -        (mapcar #'gnus-cloud-update-all chunks)
> +        (progn
> +       (mapcar #'gnus-cloud-update-all chunks)
> +       (setq gnus-cloud-sequence highest-sequence-seen))
>        chunks)))

This change means the result of the mapcar is no longer used or
returned, giving rise to the following warning:

  In gnus-cloud-download-data:
  gnus/gnus-cloud.el:482:12: Warning: ‘mapcar’ called for effect; use ‘mapc’ or
      ‘dolist’ instead

It also makes highest-sequence-seen the return value of
gnus-cloud-download-data.  Is this intended?

Thanks,

-- 
Basil