* lisp/gnus/gnus-group.el (features): Use `dlet`.
(gnus-tmp-level, gnus-tmp-marked, gnus-tmp-group): Declare vars.
(gnus-group-insert-group-line): Bind dynbound vars via `let` rather
than as formal args.  Bind `number` as dynbound.
(gnus-visual, gnus-score-find-score-files-function)
(gnus-home-score-file, gnus-apply-kill-hook)
(gnus-summary-expunge-below): Declare vars.
(gnus-group-restart, gnus-group-list-plus): Fix `interactive` spec
since the arg is unused.

* lisp/gnus/mail-source.el (mail-source-bind, mail-source-bind-common):
Use `dlet` and suppress the warnings about the non-prefixed dynbound vars.
(mail-source-set-1): Remove unused var `auth-info`.
(mail-source-call-script): Remove unused var `background`.
(mail-source-fetch-pop, mail-source-check-pop): Bind pop3 vars with `dlet`.

* lisp/gnus/gnus-int.el (mail-source-plugged, gnus-inhibit-demon):
Declare vars.
(gnus-server-opened, gnus-status-message)
(gnus-open-server, gnus-close-server, gnus-request-list)
(gnus-finish-retrieve-group-infos, gnus-retrieve-group-data-early)
(gnus-request-list-newsgroups, gnus-request-newgroups)
(gnus-request-regenerate, gnus-request-compact, gnus-request-group)
(gnus-retrieve-groups, gnus-request-post, gnus-request-expunge-group)
(gnus-request-scan, gnus-request-update-info, gnus-request-marks)
(gnus-request-accept-article, gnus-request-create-group)
(gnus-asynchronous-p, gnus-remove-denial):
Bind `gnus-command-method` via `let` rather than as formal args.

* lisp/gnus/gnus-topic.el (gnus-topic-insert-topic-line):
Pass documented vars to eval for `gnus-topic-line-format-spec`.

* lisp/gnus/message.el (message-yank-original): Use `cl-progv` rather
than `eval` to bind the vars from `message-cite-style`.

* lisp/gnus/mml.el (mml-parse-1): Use `apply` instead of `eval`.
(gnus-newsgroup-name, gnus-displaying-mime, gnus-newsgroup-name)
(gnus-article-prepare-hook, gnus-newsgroup-charset)
(gnus-original-article-buffer, gnus-message-buffer)
(message-this-is-news, message-this-is-mail): Declare vars.

* lisp/gnus/deuglify.el (gnus-outlook-rearrange-article): Remove unused
var `cite-marks`.
* lisp/gnus/gnus-art.el (ansi-color-context-region): Declare var.
(gnus-mime-display-attachment-buttons-in-header): Move declaration
before first use.
(gnus-mime-display-alternative): Remove unused var `from`.
* lisp/gnus/gnus-bookmark.el (gnus-bookmark-bmenu-list): Remove unused
var `start` `end`.
* lisp/gnus/gnus-cache.el (gnus-article-decode-hook)
(nnml-generate-active-function): Declare var.
* lisp/gnus/gnus-cite.el (gnus-message-citation-mode): Remove unused
var `keywords`.
* lisp/gnus/gnus-cloud.el (gnus-cloud-encode-data): Remove unused var
`cipher`.
(gnus-cloud-ensure-cloud-group): Remove unused var `method`.
* lisp/gnus/gnus-delay.el (gnus-delay-article): Remove unused var `days`.
* lisp/gnus/gnus-html.el (gnus-html-wash-images): Remove unused vars
`tag`, `string`, and `images`.
(gnus-html-wash-tags): Remove unused vars `string` and `images`.
* lisp/gnus/gnus-msg.el (gnus-msg-mail): Remove unused var `group-name`.
(gnus-group-mail, gnus-group-news, gnus-summary-mail-other-window)
(gnus-summary-news-other-window):
Remove unused vars `group` and `buffer`.
(gnus-configure-posting-styles): Remove unused vars `style` and `attribute`.
* lisp/gnus/gnus-picon.el (gnus-picon-find-face): Remove unused vars
`database`, `directory`, and `instance`.
(gnus-picon-transform-newsgroups): Remove unused var `point`.
* lisp/gnus/gnus-range.el (gnus-range-difference): Remove unused var `safe`.
* lisp/gnus/gnus-score.el (gnus-score-load-file): Remove unused var
`score-fn`.
* lisp/gnus/gnus-sum.el (message-options-set-recipient): Declare var.
* lisp/gnus/gnus-undo.el (gnus-undo): Fix docstring lie.
* lisp/gnus/gnus-util.el (print-string-length)
(iswitchb-make-buflist-hook): Declare vars.
(gnus-emacs-version): Remove unused var `codename`.
(gnus-rename-file): Remove unused vars `old-name` and `new-name`.
* lisp/gnus/gnus-uu.el (gnus-uu-yenc-article): Remove unused var
`start-char`.
(gnus-asynchronous): Declare var.
* lisp/gnus/mm-partial.el (gnus-displaying-mime): Declare var.
(mm-inline-partial): Remove unused var `buffer`.
* lisp/gnus/mm-view.el (w3m-force-redisplay, w3m-safe-url-regexp)
(gnus-displaying-mime, gnus-original-article-buffer)
(gnus-article-prepare-hook): Declare vars.
* lisp/gnus/mml-smime.el (mml-smime-epg-encrypt): Remove unused var
`boundary`.
(mml-smime-epg-verify): Remove unused vars `plain` and `signature-file`.
* lisp/gnus/mml1991.el (pgg-text-mode): Declare var.
* lisp/gnus/mml2015.el (pgg-text-mode): Declare var.
(mml2015-pgg-decrypt): Remove unused var `result`.
(mml2015-epg-key-image-to-string): Remove unused var `error`.
(mml2015-epg-decrypt): Remove unused var `result`.
(mml2015-epg-verify): Remove unused vars `plain` and `signature-file`.
* lisp/gnus/nnbabyl.el (nnml-current-directory): Declare var.
* lisp/gnus/nndiary.el (nndiary-files): Move declaration before first use.
* lisp/gnus/nnfolder.el (nnfolder-request-accept-article):
Remove unused var `buf`.
* lisp/gnus/nnmail.el (nnmail-parse-active): Remove unused var `err`.
* lisp/gnus/nnmairix.el (nnmairix-request-group): Remove unused var `args`.
(nnmairix-request-create-group): Remove unused var `info`.
(nnmairix-request-list): Remove unused var `folder`.
(nnmairix-request-set-mark): Remove unused var `propto`.
(nnmairix-request-set-mark): Remove unused vars `number` and `method`.
(nnmairix-close-group): Remove unused var `method`.
(nnmairix-create-search-group-from-message): Remove unused var `cq`.
(nnmairix-create-server-and-default-group): Remove unused var `create`.
(nnmairix-purge-old-groups): Remove unused var `folder`.
(nnmairix-remove-tick-mark-original-article, nnmairix-get-valid-servers):
Remove unused var `cur`.
(nnmairix-replace-group-and-numbers): Remove unused var `header`.
(nnmairix-goto-original-article): Remove unused var `rval`.
(nnmairix-widget-create-query): Remove unused var `allwidgets`.
* lisp/gnus/nnmbox.el (nnml-current-directory): Declare var.
* lisp/gnus/nnmh.el (nnmh-toplev): Move declaration before first use.
(nnmh-request-list-1): Remove unused var `rdir`.
* lisp/gnus/nnml.el (nnml-generate-nov-file): Remove unused var `file`.
* lisp/gnus/nnrss.el (nnrss-request-article): Remove unused var `post`.
(nnrss-request-article): Remove unused var `fn`.
(nnrss-check-group): Remove unused var `rdf-ns`.
* lisp/gnus/nnweb.el (nnweb-request-article): Remove unused var `active`.
(nnweb-google-parse-1): Remove unused var `Score`.
* lisp/gnus/spam-stat.el (spam-stat-error-holder): Remove var.
(spam-stat-buffer-words-with-scores): Remove unused var `word`.
(spam-stat-score-buffer): Remove unused var `spam-stat-error-holder`.
(spam-stat-split-fancy): Use `err` instead of `spam-stat-error-holder`.
* lisp/gnus/spam-wash.el (spam-wash): Remove unused var `handle`.
* lisp/gnus/spam.el (spam-copy-or-move-routine): Remove unused vars
`article` and `mark`.
(spam-register-routine): Remove unused var `article`.
(spam-log-undo-registration): Remove unused var `found`.
(spam-ifile-register-with-ifile): Remove unused var `parameters`.
(spam-check-stat): Remove unused vars `category` and `return`.
(spam-parse-list): Remove unused var `found`.
(spam-filelist-register-routine): Remove unused var `from`.

* lisp/gnus/spam-stat.el:
* lisp/gnus/spam-report.el:
* lisp/gnus/smime.el:
* lisp/gnus/nnrss.el:
* lisp/gnus/nnmairix.el:
* lisp/gnus/nnimap.el:
* lisp/gnus/nndiary.el:
* lisp/gnus/mm-url.el:
* lisp/gnus/mail-source.el:
* lisp/gnus/gnus-win.el:
* lisp/gnus/gnus-topic.el:
* lisp/gnus/gnus-sieve.el:
* lisp/gnus/gnus-search.el:
* lisp/gnus/gnus-registry.el:
* lisp/gnus/gnus-notifications.el:
* lisp/gnus/gnus-gravatar.el:
* lisp/gnus/gnus-eform.el:
* lisp/gnus/gnus-dup.el:
* lisp/gnus/gnus-diary.el:
* lisp/gnus/gnus-demon.el:
* lisp/gnus/gnus-delay.el:
* lisp/gnus/gnus-cloud.el:
* lisp/gnus/gnus-cite.el:
* lisp/gnus/gnus-bookmark.el:
* lisp/gnus/gmm-utils.el:
* lisp/gnus/deuglify.el:
* lisp/gnus/canlock.el: Remove redundant `:group` arguments

This reverts commit 20add1cd22f9775a4475148b300cf2a4de4bd54a. This
needs more work before it's ready to merge.

Previously, all Gnus backends returned header information by writing
nov lines into the nntp-server-buffer, which was later parsed.  This
commit allows the backends to return their header information as a
list of already-parsed headers, though so far none of the backends
actually do that.  The agent, cache, cloud etc. now operate on parsed
headers rather than nov text, ie. they use gnus-fetch-headers instead
of gnus-retrieve-headers.

* lisp/gnus/gnus-sum.el (gnus-fetch-headers): Handle the case in which
gnus-retrieve-headers returns headers directly.
* lisp/gnus/nnvirtual.el (nnvirtual-retrieve-headers): Use
gnus-fetch-headers rather than gnus-retrieve-headers to get headers,
meaning we're operating on already-parsed headers.
(nnvirtual-convert-headers): Remove now-unnecessary function.
(nnvirtual-update-xref-header): Rewrite to operate on parsed header.
* lisp/gnus/gnus-cloud.el (gnus-cloud-available-chunks): Use
gnus-fetch-headers instead of gnus-retrieve-headers.
* lisp/gnus/gnus-cache.el (gnus-cache-retrieve-headers): Use
gnus-fetch-headers.
(gnus-cache-braid-nov, gnus-cache-braid-heads): Delete unnecessary
functions -- we now do this work on a list of parsed headers.
* lisp/gnus/gnus-agent.el (gnus-agent-retrieve-headers): Use
gnus-fetch-headers.
(gnus-agent-braid-nov): Remove unnecessary function.
(gnus-agent-fetch-headers): Use gnus-fetch-headers.

Run "TZ=UTC0 admin/update-copyright".

* doc/misc/gnus.texi (Finding the Parent, Selection Groups)
(Searching, Basic Usage): Heed sentence-end-double-space.  Fix
formatting of prose and examples.
* etc/NEWS: Fix typo.
* lisp/gnus/gnus-srvr.el: Remove disabled autoload.
* lisp/gnus/gnus-cloud.el (gnus-cloud-available-chunks):
* lisp/gnus/gnus-group.el (gnus-group-read-ephemeral-search-group):
* lisp/gnus/gnus-sum.el (gnus-refer-thread-use-search)
(gnus-summary-refer-thread):
* lisp/gnus/gnus.el (gnus-kill-ephemeral-group):
* lisp/gnus/nnheader.el (nnheader-head-make-header)
(nnheader-parse-head):
* lisp/gnus/nnir.el:
(nnir-hyrex-remove-prefix, nnir-run-notmuch):
* lisp/gnus/nnselect.el: Fix formatting/indentation of commentary,
docstring, and/or code.

This new backend allows gnus to handle arbitrary sets of messages
spanning multiple groups, even when these groups are from different
backends and different servers. All gnus glue is removed from
nnir (leaving only the backend search functions) and gnus
search-related processing is done through nnselect. In appropriate
places 'nnir' has been replaced by 'nnselect' or 'search'.

* etc/NEWS: Document the change.
* doc/misc/gnus.texi: New  documentation for nnselect and update
searching and thread-referral  sections.
* lisp/gnus/nnselect.el: New file.
* lisp/gnus/nnir.el: Remove all gnus glue, leaving only searching
capability. Improve documentation strings.
* lisp/gnus/gnus-group.el (gnus-group-read-ephemeral-search-group,
gnus-group-make-search-group): New functions.
* lisp/gnus/gnus-msg.el (gnus-setup-message, gnus-group-news,
gnus-summary-news-other-window): Update to work for nnselect. Fix
gnus-newsgroup-name wrangling.
*lisp/gnus/gnus-registry.el
(gnus-registry-action,gnus-registry-ignore-group-p): Make work from nnselect.
* lisp/gnus/nnheader.el (nnheader-parse-head, nnheader-parse-nov):
Rework and consolidate header parsing.
* lisp/gnus/gnus-agent.el (gnus-agent-regenerate-group):
* lisp/gnus/gnus-cache.el (gnus-possibly-enter-article):
* lisp/gnus/gnus-cloud.el (gnus-cloud-available-chunks):
* lisp/gnus/gnus-msg.el (gnus-inews-yank-articles):
* lisp/gnus/gnus-sum. (gnus-get-newsgroup-headers):
* lisp/gnus/nndiary.el (nndiary-parse-head):
* lisp/gnus/nnfolder.el (nnfolder-parse-head):
* lisp/gnus/nnmaildir.el (nnmaildir--update-nov):
* lisp/gnus/nnml.el (nnml-parse-head):
* lisp/gnus/nnspool.el (nnspool-insert-nov-head):
Use new header parsing.
* lisp/gnus/gnus-start.el (gnus-read-active-for-groups): Rescan on
activation by default.
* lisp/gnus/gnus-sum.el (gnus-summary-line-format-alist): New specs
for virtual groups.
(gnus-article-sort-by-rsv, gnus-thread-sort-by-rsv):  New functions to
allow sorting by search RSV.

* lisp/gnus/gnus-cloud.el (gnus-cloud-download-data): Reindent first
argument of prog1.

* lisp/gnus/gnus-cloud.el (gnus-cloud-download-data): Return the
result of calling `gnus-cloud-update-all' when UPDATE is t, as per the
documented behaviour. (Bug#40280)

* lisp/gnus/gnus-cloud.el (gnus-cloud-download-data): Don't use
'mapcar' or effect.