21 files changed, 1651 insertions, 1222 deletions
diff --git a/doc/misc/gnus.texi b/doc/misc/gnus.texi
index 0bdc2fa297d..593f113ac14 100644
--- a/doc/misc/gnus.texi
+++ b/doc/misc/gnus.texi
@@ -641,7 +641,7 @@ Select Methods
 * Getting Mail::                Reading your personal mail with Gnus.
 * Browsing the Web::            Getting messages from a plethora of Web sources.
 * Other Sources::               Reading directories, files.
-* Combined Groups::             Combining groups into one group.
+* Virtual Groups::              Combining articles from multiple sources.
 * Email Based Diary::           Using mails to manage diary events in Gnus.
 * Gnus Unplugged::              Reading news and mail offline.
@@ -716,9 +716,10 @@ Document Groups
 * Document Server Internals::   How to add your own document types.
-Combined Groups
+Virtual Groups
-* Virtual Groups::              Combining articles from many groups.
+* Selection Groups::            Articles selected from many places.
+* Combined Groups::             Combining multiple  groups.
 Email Based Diary
@@ -10407,12 +10408,20 @@ article (@code{gnus-summary-refer-references}).
 @findex gnus-summary-refer-thread
 @kindex A T @r{(Summary)}
 Display the full thread where the current article appears
-(@code{gnus-summary-refer-thread}).  This command has to fetch all the
+(@code{gnus-summary-refer-thread}). By default this command looks for
-headers in the current group to work, so it usually takes a while.  If
+articles only in the current group. Some backends (currently only
-you do it often, you may consider setting @code{gnus-fetch-old-headers}
+'nnimap) know how to find articles in the thread directly. In other
-to @code{invisible} (@pxref{Filling In Threads}).  This won't have any
+cases each header in the current group must be fetched and examined,
-visible effects normally, but it'll make this command work a whole lot
+so it usually takes a while.  If you do it often, you may consider
-faster.  Of course, it'll make group entry somewhat slow.
+setting @code{gnus-fetch-old-headers} to @code{invisible}
+(@pxref{Filling In Threads}).  This won't have any visible effects
+normally, but it'll make this command work a whole lot faster.  Of
+course, it'll make group entry somewhat slow.
+@vindex gnus-refer-thread-use-search
+If @code{gnus-refer-thread-use-search} is non-nil then those backends
+that know how to find threads directly will search not just in the
+current group but all groups on the same server.
 @vindex gnus-refer-thread-limit
 The @code{gnus-refer-thread-limit} variable says how many old (i.e.,
@@ -10421,6 +10430,15 @@ fetch when doing this command.  The default is 200.  If @code{t}, all
 the available headers will be fetched.  This variable can be overridden
 by giving the @kbd{A T} command a numerical prefix.
+@vindex gnus-refer-thread-limit-to-thread
+In most cases @code{gnus-refer-thread} adds any articles it finds to
+the current summary buffer. (When @code{gnus-refer-thread-use-search}
+is true and the initial referral starts from a summary buffer for a
+non-virtual group this may not be possible. In this case a new summary
+buffer is created holding a virtual group with the result of the thread
+search). If @code{gnus-refer-thread-limit-to-thread} is non-nil then
+the summary buffer will be limited to articles in the thread.
 @item M-^ (Summary)
 @findex gnus-summary-refer-article
 @kindex M-^ @r{(Summary)}
@@ -13262,7 +13280,7 @@ The different methods all have their peculiarities, of course.
 * Getting Mail::                Reading your personal mail with Gnus.
 * Browsing the Web::            Getting messages from a plethora of Web sources.
 * Other Sources::               Reading directories, files.
-* Combined Groups::             Combining groups into one group.
+* Virtual Groups::              Combining articles and groups together.
 * Email Based Diary::           Using mails to manage diary events in Gnus.
 * Gnus Unplugged::              Reading news and mail offline.
 @end menu
@@ -17834,19 +17852,133 @@ methods, but want to only use secondary ones:
 @end lisp
-@node Combined Groups
+@node Virtual Groups
-@section Combined Groups
+@section Virtual Groups
-Gnus allows combining a mixture of all the other group types into bigger
+Gnus allows combining articles from many sources, and combinations of
-groups.
+whole groups together into virtual groups.
 @menu
-* Virtual Groups::              Combining articles from many groups.
+* Selection Groups::            Combining articles from many groups.
+* Combined Groups::             Combining  multiple  groups.
 @end menu
-@node Virtual Groups
+@node Selection Groups
-@subsection Virtual Groups
+@subsection Select Groups
+@cindex nnselect
+@cindex select groups
+@cindex selecting articles
+Gnus provides the @dfn{nnselect} method for creating virtual groups
+composed of collections of messages, even when these messages come
+from groups that span multiple servers and backends. For the most part
+these virtual groups behave like any other group: messages may be
+threaded, marked, moved, deleted, copied, etc.; groups may be
+ephemeral or persistent; groups may be created via
+@code{gnus-group-make-group} or browsed as foreign via
+@code{gnus-group-browse-foreign-server}.
+The key to using an nnselect group is specifying the messages to
+include. Each nnselect group has a group parameter
+@code{nnselect-specs} which is an alist with two elements: a function
+@code{nnselect-function}; and arguments @code{nnselect-args} to be
+passed to the function, if any.
+The function @code{nnselect-function} must return a vector. Each
+element of this vector is in turn a 3-element vector corresponding to
+one message. The 3 elements are: the fully-qualified group name; the
+message number; and a "score" that can be used for additional
+sorting. The values for the score are arbitrary, and are not used
+directly by the nnselect method---they may, for example, all be set to
+100.
+Here is an example:
+@lisp
+ (nnselect-specs
+  (nnselect-function . identity)
+  (nnselect-args .
+         [["nnimap+work:mail" 595 100]
+          ["nnimap+home:sent" 223 100]
+          ["nntp+news.gmane.org:gmane.emacs.gnus.general" 23666 100]]))
+@end lisp
+The function is the identity and the argument is just the list of
+messages to include in the virtual group.
+Or we may wish to create a group from the results of a search query:
+@lisp
+ (nnselect-specs
+  (nnselect-function . nnir-run-query)
+  (nnselect-args
+   (nnir-query-spec
+    (query . "FLAGGED")
+    (criteria . ""))
+   (nnir-group-spec
+    ("nnimap:home")
+    ("nnimap:work"))))
+@end lisp
+This creates a group including all flagged messages from all groups on
+two imap servers, "home" and "work".
+And one last example. Here is a function that runs a search query to
+find all message that have been received recently from certain groups:
+@lisp
+(defun my-recent-email (args)
+  (let ((query-spec
+         (list
+          (cons 'query
+                (format-time-string "SENTSINCE %d-%b-%Y"
+                                    (time-subtract (current-time)
+                                                   (days-to-time (car args)))))
+          (cons 'criteria "")))
+        (group-spec  (cadr args)))
+    (nnir-run-query   (cons 'nnir-specs
+                            (list (cons 'nnir-query-spec query-spec)
+                                  (cons 'nnir-group-spec group-spec))))))
+@end lisp
+Then an nnselect-specs
+@lisp
+ (nnselect-specs
+  (nnselect-function . my-recent-email)
+  (nnselect-args . (7 (("nnimap:home") ("nnimap:work")))))
+@end lisp
+will provide a group composed of all messages on the home and work
+servers received in the last 7 days.
+Refreshing the selection of an nnselect group by running the
+@code{nnselect-function} may take a long time to
+complete. Consequently nnselect groups are not refreshed by default
+when @code{gnus-group-get-new-news} is invoked. In those cases where
+running the function is not too time-consuming, a non-nil group
+parameter of @code{nnselect-rescan} will allow automatic refreshing. A
+refresh can always be invoked manually through
+@code{gnus-group-get-new-news-this-group}.
+The nnir interface (@pxref{nnir}) includes engines for searching a
+variety of backends. While the details of each search engine vary, the
+result of an nnir search is always a vector of the sort used by the
+nnselect method, and the results of nnir queries are usually viewed
+using an nnselect group. Indeed the standard search function
+@code{gnus-group-read-ephemeral-search-group} just creates an
+ephemeral nnselect group with the appropriate nnir query as the
+@code{nnselect-specs}.  nnir originally included both the search
+engines and the glue to connect search results to gnus. Over time this
+glue evolved into the nnselect method. The two had
+a mostly amicable parting so that nnselect could pursue its dream of
+becoming a fully functioning backend, but occasional conflicts may
+still linger.
+@node Combined Groups
+@subsection Combined Groups
 @cindex nnvirtual
 @cindex virtual groups
 @cindex merging groups
@@ -21238,14 +21370,26 @@ four days, Gnus will decay the scores four times, for instance.
 @chapter Searching
 @cindex searching
-FIXME: Add a brief overview of Gnus search capabilities.  A brief
+FIXME: A brief comparison of nnir, nnmairix, contrib/gnus-namazu would
-comparison of nnir, nnmairix, contrib/gnus-namazu would be nice
+be nice.
-as well.
+Gnus has various ways of finding articles that match certain criteria
-This chapter describes tools for searching groups and servers for
+(from a particular author, on a certain subject, etc). The simplest
-articles matching a query and then retrieving those articles.  Gnus
+method is to enter a group and then either "limit" the summary buffer
-provides a simpler mechanism for searching through articles in a summary buffer
+to the desired articles using the limiting commands (@xref{Limiting}),
-to find those matching a pattern. @xref{Searching for Articles}.
+or searching through messages in the summary buffer (@xref{Searching
+for Articles}).
+Limiting commands and summary buffer searching work on subsets of the
+articles already fetched from the servers, and these commands won’t
+query the server for additional articles.  While simple, these methods
+are therefore inadequate if the desired articles span multiple groups,
+or if the group is so large that fetching all articles is
+impractical. Many backends (such as imap, notmuch, namazu, etc.)
+provide their own facilities to search for articles directly on the
+server and gnus can take advantage of these methods.  This chapter
+describes tools for searching groups and servers for articles matching
+a query.
 @menu
 * nnir::                     Searching with various engines.
@@ -21275,7 +21419,7 @@ through mail and news repositories.  Different backends (like
 interface.
 The @code{nnimap} search engine should work with no configuration.
-Other engines require a local index that needs to be created and
+Other engines may require a local index that needs to be created and
 maintained outside of Gnus.
@@ -21283,23 +21427,19 @@ maintained outside of Gnus.
 @subsection Basic Usage
 In the group buffer typing @kbd{G G} will search the group on the
-current line by calling @code{gnus-group-make-nnir-group}.  This prompts
+current line by calling @code{gnus-group-make-search-group}.  This prompts
-for a query string, creates an ephemeral @code{nnir} group containing
+for a query string, creates an ephemeral @code{nnselect} group containing
 the articles that match this query, and takes you to a summary buffer
 showing these articles.  Articles may then be read, moved and deleted
 using the usual commands.
-The @code{nnir} group made in this way is an @code{ephemeral} group,
+The @code{nnselect} group made in this way is an @code{ephemeral}
-and some changes are not permanent: aside from reading, moving, and
+group, and will disappear upon exit from the group.  However changes
-deleting, you can't act on the original article.  But there is an
+made in the group are permanently reflected in the real groups from
-alternative: you can @emph{warp} (i.e., jump) to the original group
+which the articles are drawn.  It is occasionally convenient to view
-for the article on the current line with @kbd{A W}, aka
+articles found through searching in their original group. You can
-@code{gnus-warp-to-article}.  Even better, the function
+@emph{warp} (i.e., jump) to the original group for the article on the
-@code{gnus-summary-refer-thread}, bound by default in summary buffers
+current line with @kbd{A W}, aka @code{gnus-warp-to-article}.
-to @kbd{A T}, will first warp to the original group before it works
-its magic and includes all the articles in the thread.  From here you
-can read, move and delete articles, but also copy them, alter article
-marks, whatever.  Go nuts.
 You say you want to search more than just the group on the current line?
 No problem: just process-mark the groups you want to search.  You want
@@ -21307,14 +21447,14 @@ even more?  Calling for an nnir search with the cursor on a topic heading
 will search all the groups under that heading.
 Still not enough?  OK, in the server buffer
-@code{gnus-group-make-nnir-group} (now bound to @kbd{G}) will search all
+@code{gnus-group-make-search-group} (now bound to @kbd{G}) will search
-groups from the server on the current line.  Too much?  Want to ignore
+all groups from the server on the current line.  Too much?  Want to
-certain groups when searching, like spam groups?  Just customize
+ignore certain groups when searching, like spam groups?  Just
-@code{nnir-ignored-newsgroups}.
+customize @code{nnir-ignored-newsgroups}.
 One more thing: individual search engines may have special search
 features.  You can access these special features by giving a prefix-arg
-to @code{gnus-group-make-nnir-group}.  If you are searching multiple
+to @code{gnus-group-make-search-group}.  If you are searching multiple
 groups with different search engines you will be prompted for the
 special search features for each engine separately.
@@ -21371,8 +21511,7 @@ variable is set to use the @code{imap} engine for all servers using the
 your servers with an @code{nnimap} backend you could change this to
 @lisp
-'((nnimap . namazu)
+'((nnimap . namazu))
-  (nntp . gmane))
 @end lisp
 @node The imap Engine
@@ -21575,7 +21714,7 @@ This engine is obsolete.
 @item nnir-method-default-engines
 Alist of pairs of server backends and search engines.  The default
-associations are
+association is
 @example
 (nnimap . imap)
 @end example
@@ -21584,32 +21723,6 @@ associations are
 A regexp to match newsgroups in the active file that should be skipped
 when searching all groups on a server.
-@item nnir-summary-line-format
-The format specification to be used for lines in an nnir summary buffer.
-All the items from @code{gnus-summary-line-format} are available, along with
-three items unique to nnir summary buffers:
-@example
-%Z    Search retrieval score value (integer)
-%G    Article original full group name (string)
-%g    Article original short group name (string)
-@end example
-If @code{nil} (the default) this will use @code{gnus-summary-line-format}.
-@item nnir-retrieve-headers-override-function
-If non-@code{nil}, a function that retrieves article headers rather than using
-the gnus built-in function.  This function takes an article list and
-group as arguments and populates the @code{nntp-server-buffer} with the
-retrieved headers.  It should then return either 'nov or 'headers
-indicating the retrieved header format.  Failure to retrieve headers
-should return @code{nil}.
-If this variable is @code{nil}, or if the provided function returns
-@code{nil} for a search result, @code{gnus-retrieve-headers} will be
-called instead."
 @end table
diff --git a/etc/NEWS b/etc/NEWS
index e0ea8f53cc8..da3928d6e49 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -317,7 +317,24 @@ tags to be considered as well.
 ** Gnus
 +++
-*** New user option 'gnus-dbus-close-on-sleep'.
+*** New backend 'nnselect'
+The newly added nnselect backend allows creating groups from an
+arbitrary list of articles that may come from multiple groups and
+servers. These groups generally behave like any other group: they may
+be ephemeral or persistent, and allow article marking, moving,
+deletion, etc. Nnselect groups may be created like any other group,
+but there is also a convenience function for the common case of
+obtaining the list of articles as a result of a search:
+'gnus-group-make-search-group' (G g) that will prompt for an nnir
+search query and create a dedicated group for that search.  As part of
+this addition, the variable 'nnir-summary-line-format' has been
+removed; it's functionality is now available directly in the
+'gnus-summary-line-format' 'G' and 'g' specs. The variable
+'gnus-refer-thread-use-nnir' has been renamed
+'gnus-refer-thread-use-search'.
+++
+*** New user option 'gnus-dbus-close-on-sleep'
 On systems with D-Bus support, it is now possible to register a signal
 to close all Gnus servers before the system sleeps.
diff --git a/lisp/gnus/gnus-agent.el b/lisp/gnus/gnus-agent.el
index 88873f47bd5..03e447e072a 100644
--- a/lisp/gnus/gnus-agent.el
+++ b/lisp/gnus/gnus-agent.el
@@ -3934,7 +3934,7 @@ If REREAD is not nil, downloaded articles are marked as unread."
                   (mm-with-unibyte-buffer
                     (nnheader-insert-file-contents file)
                     (nnheader-remove-body)
-                     (setq header (nnheader-parse-naked-head)))
+                     (setq header (nnheader-parse-head t)))
                   (setf (mail-header-number header) (car downloaded))
                   (if nov-arts
                       (let ((key (concat "^" (int-to-string (car nov-arts))
diff --git a/lisp/gnus/gnus-cache.el b/lisp/gnus/gnus-cache.el
index 02a8ea723d3..7ca3bf1ce1c 100644
--- a/lisp/gnus/gnus-cache.el
+++ b/lisp/gnus/gnus-cache.el
@@ -186,7 +186,7 @@ it's not cached."
                (gnus-cache-update-file-total-fetched-for group file))
              (setq lines-chars (nnheader-get-lines-and-char))
              (nnheader-remove-body)
-              (setq headers (nnheader-parse-naked-head))
+              (setq headers (nnheader-parse-head t))
              (setf (mail-header-number headers) number)
              (setf (mail-header-lines headers) (car lines-chars))
              (setf (mail-header-chars headers) (cadr lines-chars))
diff --git a/lisp/gnus/gnus-cloud.el b/lisp/gnus/gnus-cloud.el
index 673a4d22988..e40b2eb418d 100644
--- a/lisp/gnus/gnus-cloud.el
+++ b/lisp/gnus/gnus-cloud.el
@@ -391,6 +391,8 @@ When FULL is t, upload everything, not just a difference from the last full."
            (gnus-group-refresh-group group))
        (gnus-error 2 "Failed to upload Gnus Cloud data to %s" group)))))
+(defvar gnus-alter-header-function)
 (defun gnus-cloud-add-timestamps (elems)
  (dolist (elem elems)
    (let* ((file-name (plist-get elem :file-name))
@@ -409,9 +411,11 @@ When FULL is t, upload everything, not just a difference from the last full."
    (when (gnus-retrieve-headers (gnus-uncompress-range active) group)
      (with-current-buffer nntp-server-buffer
        (goto-char (point-min))
-        (while (and (not (eobp))
+        (while (setq head (nnheader-parse-head))
-                    (setq head (nnheader-parse-head)))
+          (when gnus-alter-header-function
-          (push head headers))))
+            (funcall gnus-alter-header-function head))
+          (push head headers))
+        ))
    (sort (nreverse headers)
          (lambda (h1 h2)
            (> (gnus-cloud-chunk-sequence (mail-header-subject h1))
diff --git a/lisp/gnus/gnus-group.el b/lisp/gnus/gnus-group.el
index 2cbbe624602..ad6e0e30bca 100644
--- a/lisp/gnus/gnus-group.el
+++ b/lisp/gnus/gnus-group.el
@@ -49,8 +49,6 @@
 (autoload 'gnus-agent-total-fetched-for "gnus-agent")
 (autoload 'gnus-cache-total-fetched-for "gnus-cache")
-(autoload 'gnus-group-make-nnir-group "nnir")
 (autoload 'gnus-cloud-upload-all-data "gnus-cloud")
 (autoload 'gnus-cloud-download-all-data "gnus-cloud")
@@ -663,7 +661,8 @@ simple manner."
  "D" gnus-group-enter-directory
  "f" gnus-group-make-doc-group
  "w" gnus-group-make-web-group
-  "G" gnus-group-make-nnir-group
+  "G" gnus-group-read-ephemeral-search-group
+  "g" gnus-group-make-search-group
  "M" gnus-group-read-ephemeral-group
  "r" gnus-group-rename-group
  "R" gnus-group-make-rss-group
@@ -909,7 +908,8 @@ simple manner."
        ["Add the help group" gnus-group-make-help-group t]
        ["Make a doc group..." gnus-group-make-doc-group t]
        ["Make a web group..." gnus-group-make-web-group t]
-        ["Make a search group..." gnus-group-make-nnir-group t]
+        ["Read a search group..." gnus-group-read-ephemeral-search-group t]
+        ["Make a search group..." gnus-group-make-search-group t]
        ["Make a virtual group..." gnus-group-make-empty-virtual t]
        ["Add a group to a virtual..." gnus-group-add-to-virtual t]
        ["Make an ephemeral group..." gnus-group-read-ephemeral-group t]
@@ -3166,6 +3166,52 @@ mail messages or news articles in files that have numeric names."
     (gnus-group-real-name group)
     (list 'nndir (gnus-group-real-name group) (list 'nndir-directory dir)))))
+(autoload 'nnir-make-specs "nnir")
+(autoload 'gnus-group-topic-name "gnus-topic")
+;; Temporary to make group creation easier
+(defun gnus-group-make-search-group (nnir-extra-parms &optional specs)
+  (interactive "P")
+  (let ((name (gnus-read-group "Group name: ")))
+    (with-current-buffer gnus-group-buffer
+      (gnus-group-make-group
+       name
+       (list 'nnselect "nnselect")
+       nil
+       (list
+        (cons 'nnselect-specs
+              (list
+               (cons 'nnselect-function 'nnir-run-query)
+               (cons 'nnselect-args
+                     (nnir-make-specs nnir-extra-parms specs)))))))))
+(defun gnus-group-read-ephemeral-search-group (nnir-extra-parms &optional specs)
+  "Create an nnselect group based on a search.  Prompt for a
+search query and determine the groups to search as follows: if
+called from the *Server* buffer search all groups belonging to
+the server on the current line; if called from the *Group* buffer
+search any marked groups, or the group on the current line, or
+all the groups under the current topic. Calling with a prefix-arg
+prompts for additional search-engine specific constraints. A
+non-nil `specs' arg must be an alist with `nnir-query-spec' and
+`nnir-group-spec' keys, and skips all prompting."
+  (interactive "P")
+  (gnus-group-read-ephemeral-group
+   (concat "nnselect-" (message-unique-id))
+   (list 'nnselect "nnselect")
+   nil
+   (cons (current-buffer) gnus-current-window-configuration)
+                                        ;     nil
+   nil nil
+   (list
+    (cons 'nnselect-specs
+          (list
+           (cons 'nnselect-function 'nnir-run-query)
+           (cons 'nnselect-args
+                 (nnir-make-specs nnir-extra-parms specs))))
+    (cons 'nnselect-artlist nil))))
 (defun gnus-group-add-to-virtual (n vgroup)
  "Add the current group to a virtual group."
  (interactive
diff --git a/lisp/gnus/gnus-msg.el b/lisp/gnus/gnus-msg.el
index e770abc2cdf..7bc7fb5be41 100644
--- a/lisp/gnus/gnus-msg.el
+++ b/lisp/gnus/gnus-msg.el
@@ -393,10 +393,9 @@ only affect the Gcc copy, but not the original message."
     (gnus-inews-make-draft-meta-information
      ,gnus-newsgroup-name ',articles)))
-(autoload 'nnir-article-number "nnir" nil nil 'macro)
+(autoload 'nnselect-article-number "nnselect" nil nil 'macro)
-(autoload 'nnir-article-group "nnir" nil nil 'macro)
+(autoload 'nnselect-article-group "nnselect" nil nil 'macro)
-(autoload 'gnus-nnir-group-p "nnir")
+(autoload 'gnus-nnselect-group-p "nnselect")
 (defvar gnus-article-reply nil)
 (defmacro gnus-setup-message (config &rest forms)
@@ -404,22 +403,24 @@ only affect the Gcc copy, but not the original message."
        (winconf-name (make-symbol "gnus-setup-message-winconf-name"))
        (buffer (make-symbol "gnus-setup-message-buffer"))
        (article (make-symbol "gnus-setup-message-article"))
+        (oarticle (make-symbol "gnus-setup-message-oarticle"))
        (yanked (make-symbol "gnus-setup-yanked-articles"))
        (group (make-symbol "gnus-setup-message-group")))
    `(let ((,winconf (current-window-configuration))
           (,winconf-name gnus-current-window-configuration)
           (,buffer (buffer-name (current-buffer)))
-           (,article (if (and (gnus-nnir-group-p gnus-newsgroup-name)
+           (,article   (when gnus-article-reply
-                              gnus-article-reply)
+                         (or (nnselect-article-number
-                         (nnir-article-number (or (car-safe gnus-article-reply)
+                              (or (car-safe gnus-article-reply)
-                                                  gnus-article-reply))
+                                  gnus-article-reply))
-                       gnus-article-reply))
+                             gnus-article-reply)))
+           (,oarticle gnus-article-reply)
           (,yanked gnus-article-yanked-articles)
-           (,group (if (and (gnus-nnir-group-p gnus-newsgroup-name)
+           (,group (when gnus-article-reply
-                            gnus-article-reply)
+                     (or (nnselect-article-group
-                       (nnir-article-group (or (car-safe gnus-article-reply)
+                          (or (car-safe gnus-article-reply)
-                                               gnus-article-reply))
+                              gnus-article-reply))
-                     gnus-newsgroup-name))
+                         gnus-newsgroup-name)))
           (message-header-setup-hook
            (copy-sequence message-header-setup-hook))
           (mbl mml-buffer-list)
@@ -460,24 +461,23 @@ only affect the Gcc copy, but not the original message."
       (unwind-protect
           (progn
             ,@forms)
-         (gnus-inews-add-send-actions ,winconf ,buffer ,article ,config
+         (gnus-inews-add-send-actions ,winconf ,buffer ,oarticle ,config
                                      ,yanked ,winconf-name)
         (setq gnus-message-buffer (current-buffer))
         (set (make-local-variable 'gnus-message-group-art)
              (cons ,group ,article))
-         (set (make-local-variable 'gnus-newsgroup-name) ,group)
+         ;; Enable highlighting of different citation levels
-         ;; Enable highlighting of different citation levels
+         (when gnus-message-highlight-citation
-         (when gnus-message-highlight-citation
+           (gnus-message-citation-mode 1))
-           (gnus-message-citation-mode 1))
+         (gnus-run-hooks 'gnus-message-setup-hook)
-         (gnus-run-hooks 'gnus-message-setup-hook)
+         (if (eq major-mode 'message-mode)
-         (if (eq major-mode 'message-mode)
+             (let ((mbl1 mml-buffer-list))
-             (let ((mbl1 mml-buffer-list))
+               (setq mml-buffer-list mbl)  ;; Global value
-               (setq mml-buffer-list mbl)  ;; Global value
+               (set (make-local-variable 'mml-buffer-list) mbl1);; Local value
-               (set (make-local-variable 'mml-buffer-list) mbl1);; Local value
+               (add-hook 'change-major-mode-hook 'mml-destroy-buffers nil t)
-               (add-hook 'change-major-mode-hook 'mml-destroy-buffers nil t)
+               (add-hook 'kill-buffer-hook 'mml-destroy-buffers t t))
-               (add-hook 'kill-buffer-hook 'mml-destroy-buffers t t))
+           (mml-destroy-buffers)
-           (mml-destroy-buffers)
+           (setq mml-buffer-list mbl)))
-           (setq mml-buffer-list mbl)))
       (message-hide-headers)
       (gnus-add-buffer)
       (gnus-configure-windows ,config t)
@@ -521,12 +521,10 @@ instead."
          mail-buf)
      (unwind-protect
          (progn
-            (setq gnus-newsgroup-name "")
+            (let ((gnus-newsgroup-name ""))
            (gnus-setup-message 'message
              (message-mail to subject other-headers continue
-                            nil yank-action send-actions return-action)))
+                            nil yank-action send-actions return-action)))))
-        (with-current-buffer buf
-          (setq gnus-newsgroup-name group-name)))
      (when switch-action
        (setq mail-buf (current-buffer))
        (switch-to-buffer buf)
@@ -617,18 +615,15 @@ If ARG is 1, prompt for a group name to find the posting style."
        (buffer (current-buffer)))
    (unwind-protect
        (progn
-          (setq gnus-newsgroup-name
+          (let ((gnus-newsgroup-name
-                (if arg
+                 (if arg
-                    (if (= 1 (prefix-numeric-value arg))
+                     (if (= 1 (prefix-numeric-value arg))
-                        (gnus-group-completing-read
+                         (gnus-group-completing-read
-                         "Use posting style of group"
+                          "Use posting style of group"
-                         nil (gnus-read-active-file-p))
+                          nil (gnus-read-active-file-p))
-                      (gnus-group-group-name))
+                       (gnus-group-group-name))
-                  ""))
+                   "")))
-          ;; #### see comment in gnus-setup-message -- drv
+            (gnus-setup-message 'message (message-mail)))))))
-          (gnus-setup-message 'message (message-mail)))
-      (with-current-buffer buffer
-        (setq gnus-newsgroup-name group)))))
 (defun gnus-group-news (&optional arg)
  "Start composing a news.
@@ -647,19 +642,16 @@ network.  The corresponding back end must have a `request-post' method."
        (buffer (current-buffer)))
    (unwind-protect
        (progn
-          (setq gnus-newsgroup-name
+          (let ((gnus-newsgroup-name
                (if arg
                    (if (= 1 (prefix-numeric-value arg))
                        (gnus-group-completing-read "Use group"
                                                    nil
                                                    (gnus-read-active-file-p))
                      (gnus-group-group-name))
-                  ""))
+                  "")))
-          ;; #### see comment in gnus-setup-message -- drv
          (gnus-setup-message 'message
-            (message-news (gnus-group-real-name gnus-newsgroup-name))))
+            (message-news (gnus-group-real-name gnus-newsgroup-name))))))))
-      (with-current-buffer buffer
-        (setq gnus-newsgroup-name group)))))
 (defun gnus-group-post-news (&optional arg)
  "Start composing a message (a news by default).
@@ -694,18 +686,15 @@ posting style."
        (buffer (current-buffer)))
    (unwind-protect
        (progn
-          (setq gnus-newsgroup-name
+          (let ((gnus-newsgroup-name
                (if arg
                    (if (= 1 (prefix-numeric-value arg))
                        (gnus-group-completing-read "Use group"
                                                    nil
                                                    (gnus-read-active-file-p))
                      "")
-                  gnus-newsgroup-name))
+                  gnus-newsgroup-name)))
-          ;; #### see comment in gnus-setup-message -- drv
+          (gnus-setup-message 'message (message-mail)))))))
-          (gnus-setup-message 'message (message-mail)))
-      (with-current-buffer buffer
-        (setq gnus-newsgroup-name group)))))
 (defun gnus-summary-news-other-window (&optional arg)
  "Start composing a news in another window.
@@ -724,24 +713,21 @@ network.  The corresponding back end must have a `request-post' method."
        (buffer (current-buffer)))
    (unwind-protect
        (progn
-          (setq gnus-newsgroup-name
+          (let ((gnus-newsgroup-name
                (if arg
                    (if (= 1 (prefix-numeric-value arg))
                        (gnus-group-completing-read "Use group"
                                                    nil
                                                    (gnus-read-active-file-p))
                      "")
-                  gnus-newsgroup-name))
+                  gnus-newsgroup-name)))
-          ;; #### see comment in gnus-setup-message -- drv
          (gnus-setup-message 'message
            (progn
              (message-news (gnus-group-real-name gnus-newsgroup-name))
              (set (make-local-variable 'gnus-discouraged-post-methods)
                   (remove
                    (car (gnus-find-method-for-group gnus-newsgroup-name))
-                    gnus-discouraged-post-methods)))))
+                    gnus-discouraged-post-methods)))))))))
-      (with-current-buffer buffer
-        (setq gnus-newsgroup-name group)))))
 (defun gnus-summary-post-news (&optional arg)
  "Start composing a message.  Post to the current group by default.
@@ -823,7 +809,7 @@ active, the entire article will be yanked."
             (with-current-buffer gnus-article-copy
               (save-restriction
                 (nnheader-narrow-to-headers)
-                 (nnheader-parse-naked-head)))))
+                 (nnheader-parse-head t)))))
        (message-yank-original)
        (message-exchange-point-and-mark)
        (setq beg (or beg (mark t))))
@@ -1993,10 +1979,10 @@ process-mark several articles, they will all be attached."
    (gnus-summary-iterate n
      (gnus-summary-select-article)
      (with-current-buffer destination
-       ;; Attach at the end of the buffer.
+        ;; Attach at the end of the buffer.
-       (save-excursion
+        (save-excursion
-         (goto-char (point-max))
+          (goto-char (point-max))
-         (message-forward-make-body-mime gnus-original-article-buffer))))
+          (message-forward-make-body-mime gnus-original-article-buffer))))
    (gnus-configure-windows 'message t)))
 (provide 'gnus-msg)
diff --git a/lisp/gnus/gnus-registry.el b/lisp/gnus/gnus-registry.el
index 1ac1d05e033..65bcd0e8a36 100644
--- a/lisp/gnus/gnus-registry.el
+++ b/lisp/gnus/gnus-registry.el
@@ -427,6 +427,8 @@ This is not required after changing `gnus-registry-cache-file'."
    (gnus-message 4 "Removed %d ignored entries from the Gnus registry"
                  (- old-size (registry-size db)))))
+(declare-function gnus-nnselect-group-p "nnselect" (group))
+(declare-function nnselect-article-group "nnselect" (article))
 ;; article move/copy/spool/delete actions
 (defun gnus-registry-action (action data-header from &optional to method)
  (let* ((id (mail-header-id data-header))
@@ -437,7 +439,10 @@ This is not required after changing `gnus-registry-cache-file'."
                      (or (cdr-safe (assq 'To extra)) "")))
         (sender (nth 0 (gnus-registry-extract-addresses
                         (mail-header-from data-header))))
-         (from (gnus-group-guess-full-name-from-command-method from))
+         (from (gnus-group-guess-full-name-from-command-method
+                (if (gnus-nnselect-group-p from)
+                    (nnselect-article-group (mail-header-number data-header))
+                  from)))
         (to (if to (gnus-group-guess-full-name-from-command-method to) nil)))
    (gnus-message 7 "Gnus registry: article %s %s from %s to %s"
                  id (if method "respooling" "going") from to)
@@ -788,7 +793,7 @@ Consults `gnus-registry-unfollowed-groups' and
 Consults `gnus-registry-ignored-groups' and
 `nnmail-split-fancy-with-parent-ignore-groups'."
  (and group
-       (or (gnus-grep-in-list
+       (or (gnus-virtual-group-p group) (gnus-grep-in-list
            group
            (delq nil (mapcar (lambda (g)
                                (cond
@@ -1218,7 +1223,7 @@ is `ask', ask the user; or if `gnus-registry-install' is non-nil, enable it."
      (gnus-registry-initialize)))
  gnus-registry-enabled)
-;; largely based on nnir-warp-to-article
+;; largely based on nnselect-warp-to-article
 (defun gnus-try-warping-via-registry ()
  "Try to warp via the registry.
 This will be done via the current article's source group based on
@@ -1242,7 +1247,7 @@ data stored in the registry."
                      (gnus-ephemeral-group-p group) ;; any ephemeral group
                      (memq (car (gnus-find-method-for-group group))
                            ;; Specific methods; this list may need to expand.
-                            '(nnir)))
+                            '(nnselect)))
            ;; remember that we've seen this group already
            (push group seen-groups)
diff --git a/lisp/gnus/gnus-srvr.el b/lisp/gnus/gnus-srvr.el
index 095e05408d6..8cb80b2f520 100644
--- a/lisp/gnus/gnus-srvr.el
+++ b/lisp/gnus/gnus-srvr.el
@@ -34,7 +34,8 @@
 (require 'gnus-range)
 (require 'gnus-cloud)
-(autoload 'gnus-group-make-nnir-group "nnir")
+(autoload 'gnus-group-read-ephemeral-search-group "nnselect")
+;;(autoload 'gnus-group-make-permanent-search-group "nnselect")
 (defcustom gnus-server-exit-hook nil
  "Hook run when exiting the server buffer."
@@ -176,7 +177,7 @@ If nil, a faster, but more primitive, buffer is used instead."
    "g" gnus-server-regenerate-server
-    "G" gnus-group-make-nnir-group
+    "G" gnus-group-read-ephemeral-search-group
    "z" gnus-server-compact-server
diff --git a/lisp/gnus/gnus-start.el b/lisp/gnus/gnus-start.el
index fe600f107ce..e4f05de5f8e 100644
--- a/lisp/gnus/gnus-start.el
+++ b/lisp/gnus/gnus-start.el
@@ -1802,7 +1802,7 @@ backend check whether the group actually exists."
     ;; by one.
     (t
      (dolist (info infos)
-        (gnus-activate-group (gnus-info-group info) nil nil method t))))))
+        (gnus-activate-group (gnus-info-group info) t nil method t))))))
 (defun gnus-make-hashtable-from-newsrc-alist ()
  "Create a hash table from `gnus-newsrc-alist'.
diff --git a/lisp/gnus/gnus-sum.el b/lisp/gnus/gnus-sum.el
index c53f81fe026..8f37fc88284 100644
--- a/lisp/gnus/gnus-sum.el
+++ b/lisp/gnus/gnus-sum.el
@@ -85,8 +85,8 @@
 (autoload 'gnus-article-outlook-unwrap-lines "deuglify" nil t)
 (autoload 'gnus-article-outlook-repair-attribution "deuglify" nil t)
 (autoload 'gnus-article-outlook-rearrange-citation "deuglify" nil t)
-(autoload 'nnir-article-rsv "nnir" nil nil 'macro)
+(autoload 'nnselect-article-rsv "nnselect" nil nil)
-(autoload 'nnir-article-group "nnir" nil nil 'macro)
+(autoload 'nnselect-article-group "nnselect" nil nil)
 (defcustom gnus-kill-summary-on-exit t
  "If non-nil, kill the summary buffer when you exit from it.
@@ -144,9 +144,9 @@ If t, fetch all the available old headers."
  :type '(choice number
                 (sexp :menu-tag "other" t)))
-(defcustom gnus-refer-thread-use-nnir nil
+(defcustom gnus-refer-thread-use-search nil
-  "Use nnir to search an entire server when referring threads.
+  "Search an entire server when referring threads. A
-A nil value will only search for thread-related articles in the
+nil value will only search for thread-related articles in the
 current group."
  :version "24.1"
  :group 'gnus-thread
@@ -884,6 +884,7 @@ controls how articles are sorted."
                          (function-item gnus-article-sort-by-subject)
                          (function-item gnus-article-sort-by-date)
                          (function-item gnus-article-sort-by-score)
+                          (function-item gnus-article-sort-by-rsv)
                          (function-item gnus-article-sort-by-random)
                          (function :tag "other"))
                  (boolean :tag "Reverse order"))))
@@ -927,6 +928,7 @@ subthreads, customize `gnus-subthread-sort-functions'."
                   (function-item gnus-thread-sort-by-subject)
                   (function-item gnus-thread-sort-by-date)
                   (function-item gnus-thread-sort-by-score)
+                   (function-item gnus-thread-sort-by-rsv)
                   (function-item gnus-thread-sort-by-most-recent-number)
                   (function-item gnus-thread-sort-by-most-recent-date)
                   (function-item gnus-thread-sort-by-random)
@@ -1433,16 +1435,13 @@ the normal Gnus MIME machinery."
    (?c (or (mail-header-chars gnus-tmp-header) 0) ?d)
    (?k (gnus-summary-line-message-size gnus-tmp-header) ?s)
    (?L gnus-tmp-lines ?s)
-    (?Z (or (nnir-article-rsv (mail-header-number gnus-tmp-header))
+    (?Z (or (nnselect-article-rsv (mail-header-number gnus-tmp-header))
-            0)
+            0) ?d)
-        ?d)
+    (?G (or (nnselect-article-group (mail-header-number gnus-tmp-header))
-    (?G (or (nnir-article-group (mail-header-number gnus-tmp-header))
+            "") ?s)
-            "")
-        ?s)
    (?g (or (gnus-group-short-name
-             (nnir-article-group (mail-header-number gnus-tmp-header)))
+             (nnselect-article-group (mail-header-number gnus-tmp-header)))
-            "")
+            "") ?s)
-        ?s)
    (?O gnus-tmp-downloaded ?c)
    (?I gnus-tmp-indentation ?s)
    (?T (if (= gnus-tmp-level 0) "" (make-string (frame-width) ? )) ?s)
@@ -1619,6 +1618,8 @@ This list will always be a subset of gnus-newsgroup-undownloaded.")
 (defvar gnus-newsgroup-sparse nil)
+(defvar gnus-newsgroup-selection nil)
 (defvar gnus-current-article nil)
 (defvar gnus-article-current nil)
 (defvar gnus-current-headers nil)
@@ -1653,6 +1654,8 @@ This list will always be a subset of gnus-newsgroup-undownloaded.")
    gnus-newsgroup-undownloaded
    gnus-newsgroup-unsendable
+    gnus-newsgroup-selection
    gnus-newsgroup-begin gnus-newsgroup-end
    gnus-newsgroup-last-rmail gnus-newsgroup-last-mail
    gnus-newsgroup-last-folder gnus-newsgroup-last-file
@@ -4532,48 +4535,14 @@ Returns HEADER if it was entered in the DEPENDENCIES.  Returns nil otherwise."
 ;; This function has to be called with point after the article number
 ;; on the beginning of the line.
 (defsubst gnus-nov-parse-line (number dependencies &optional force-new)
-  (let ((eol (point-at-eol))
+  (let (header)
-        header references in-reply-to)
    ;; overview: [num subject from date id refs chars lines misc]
    (unwind-protect
-        (let (x)
+        (narrow-to-region (point) (point-at-eol))
-          (narrow-to-region (point) eol)
+      (unless (eobp)
-          (unless (eobp)
+        (forward-char))
-            (forward-char))
+      (setq header (nnheader-parse-nov number))
-          (setq header
-                (make-full-mail-header
-                 number                 ; number
-                 (condition-case ()     ; subject
-                     (gnus-remove-odd-characters
-                      (funcall gnus-decode-encoded-word-function
-                               (setq x (nnheader-nov-field))))
-                   (error x))
-                 (condition-case ()     ; from
-                     (gnus-remove-odd-characters
-                      (funcall gnus-decode-encoded-address-function
-                               (setq x (nnheader-nov-field))))
-                   (error x))
-                 (nnheader-nov-field)   ; date
-                 (nnheader-nov-read-message-id number)  ; id
-                 (setq references (nnheader-nov-field)) ; refs
-                 (nnheader-nov-read-integer) ; chars
-                 (nnheader-nov-read-integer) ; lines
-                 (unless (eobp)
-                   (if (looking-at "Xref: ")
-                       (goto-char (match-end 0)))
-                   (nnheader-nov-field)) ; Xref
-                 (nnheader-nov-parse-extra)))) ; extra
      (widen))
-    (when (and (string= references "")
-               (setq in-reply-to (mail-header-extra header))
-               (setq in-reply-to (cdr (assq 'In-Reply-To in-reply-to))))
-      (setf (mail-header-references header)
-            (gnus-extract-message-id-from-in-reply-to in-reply-to)))
    (when gnus-alter-header-function
      (funcall gnus-alter-header-function header))
    (gnus-dependencies-add-header header dependencies force-new)))
@@ -5104,6 +5073,17 @@ using some other form will lead to serious barfage."
  (gnus-article-sort-by-date
   (gnus-thread-header h1) (gnus-thread-header h2)))
+(defsubst gnus-article-sort-by-rsv (h1 h2)
+  "Sort articles by rsv."
+  (when gnus-newsgroup-selection
+    (< (nnselect-article-rsv (mail-header-number h1))
+       (nnselect-article-rsv (mail-header-number h2)))))
+(defun gnus-thread-sort-by-rsv (h1 h2)
+  "Sort threads by root article rsv."
+  (gnus-article-sort-by-rsv
+   (gnus-thread-header h1) (gnus-thread-header h2)))
 (defsubst gnus-article-sort-by-score (h1 h2)
  "Sort articles by root article score.
 Unscored articles will be counted as having a score of zero."
@@ -5634,22 +5614,32 @@ or a straight list of headers."
  "Fetch headers of ARTICLES."
  (gnus-message 7 "Fetching headers for %s..." gnus-newsgroup-name)
  (prog1
-      (if (eq 'nov
+      (pcase (setq gnus-headers-retrieved-by
-              (setq gnus-headers-retrieved-by
+                   (gnus-retrieve-headers
-                    (gnus-retrieve-headers
+                    articles gnus-newsgroup-name
-                     articles gnus-newsgroup-name
+                    (or limit
-                     (or limit
+                        ;; We might want to fetch old headers, but
-                         ;; We might want to fetch old headers, but
+                        ;; not if there is only 1 article.
-                         ;; not if there is only 1 article.
+                        (and (or (and
-                         (and (or (and
+                                  (not (eq gnus-fetch-old-headers 'some))
-                                   (not (eq gnus-fetch-old-headers 'some))
+                                  (not (numberp gnus-fetch-old-headers)))
-                                   (not (numberp gnus-fetch-old-headers)))
+                                 (> (length articles) 1))
-                                  (> (length articles) 1))
+                             gnus-fetch-old-headers))))
-                              gnus-fetch-old-headers)))))
+    ('nov
-          (gnus-get-newsgroup-headers-xover
+     (gnus-get-newsgroup-headers-xover
-           articles force-new dependencies gnus-newsgroup-name t)
+      articles force-new dependencies gnus-newsgroup-name t))
-        (gnus-get-newsgroup-headers dependencies force-new))
+    ('headers
-    (gnus-message 7 "Fetching headers for %s...done" gnus-newsgroup-name)))
+     (gnus-get-newsgroup-headers dependencies force-new))
+    ((pred listp)
+     (let ((dependencies
+            (or dependencies
+                (with-current-buffer gnus-summary-buffer
+                  gnus-newsgroup-dependencies))))
+     (delq nil (mapcar   #'(lambda (header)
+                             (gnus-dependencies-add-header
+                              header dependencies force-new))
+                         gnus-headers-retrieved-by)))))
+  (gnus-message 7 "Fetching headers for %s...done" gnus-newsgroup-name)))
 (defun gnus-select-newsgroup (group &optional read-all select-articles)
  "Select newsgroup GROUP.
@@ -6405,12 +6395,11 @@ The resulting hash table is returned, or nil if no Xrefs were found."
          (gnus-group-update-group group t))))))
 (defun gnus-get-newsgroup-headers (&optional dependencies force-new)
-  (let ((cur nntp-server-buffer)
+  (let ((dependencies
-        (dependencies
         (or dependencies
             (with-current-buffer gnus-summary-buffer
               gnus-newsgroup-dependencies)))
-        headers id end ref number
+        headers
        (mail-parse-charset gnus-newsgroup-charset)
        (mail-parse-ignored-charsets
         (save-current-buffer (condition-case nil
@@ -6418,146 +6407,15 @@ The resulting hash table is returned, or nil if no Xrefs were found."
                                (error))
                              gnus-newsgroup-ignored-charsets)))
    (with-current-buffer nntp-server-buffer
-      ;; Translate all TAB characters into SPACE characters.
-      (subst-char-in-region (point-min) (point-max) ?\t ?  t)
-      (subst-char-in-region (point-min) (point-max) ?\r ?  t)
-      (ietf-drums-unfold-fws)
      (gnus-run-hooks 'gnus-parse-headers-hook)
-      (let ((case-fold-search t)
+      (let ((nnmail-extra-headers gnus-extra-headers)
-            in-reply-to header p lines chars)
+            header)
        (goto-char (point-min))
-        ;; Search to the beginning of the next header.  Error messages
+        (while (setq header (nnheader-parse-head))
-        ;; do not begin with 2 or 3.
-        (while (re-search-forward "^[23][0-9]+ " nil t)
-          (setq id nil
-                ref nil)
-          ;; This implementation of this function, with nine
-          ;; search-forwards instead of the one re-search-forward and
-          ;; a case (which basically was the old function) is actually
-          ;; about twice as fast, even though it looks messier.  You
-          ;; can't have everything, I guess.  Speed and elegance
-          ;; doesn't always go hand in hand.
-          (setq
-           header
-           (make-full-mail-header
-            ;; Number.
-            (prog1
-                (setq number (read cur))
-              (end-of-line)
-              (setq p (point))
-              (narrow-to-region (point)
-                                (or (and (search-forward "\n.\n" nil t)
-                                         (- (point) 2))
-                                    (point))))
-            ;; Subject.
-            (progn
-              (goto-char p)
-              (if (search-forward "\nsubject:" nil t)
-                  (funcall gnus-decode-encoded-word-function
-                           (nnheader-header-value))
-                "(none)"))
-            ;; From.
-            (progn
-              (goto-char p)
-              (if (search-forward "\nfrom:" nil t)
-                  (funcall gnus-decode-encoded-address-function
-                           (nnheader-header-value))
-                "(nobody)"))
-            ;; Date.
-            (progn
-              (goto-char p)
-              (if (search-forward "\ndate:" nil t)
-                  (nnheader-header-value) ""))
-            ;; Message-ID.
-            (progn
-              (goto-char p)
-              (setq id (if (re-search-forward
-                            "^message-id: *\\(<[^\n\t> ]+>\\)" nil t)
-                           ;; We do it this way to make sure the Message-ID
-                           ;; is (somewhat) syntactically valid.
-                           (buffer-substring (match-beginning 1)
-                                             (match-end 1))
-                         ;; If there was no message-id, we just fake one
-                         ;; to make subsequent routines simpler.
-                         (nnheader-generate-fake-message-id number))))
-            ;; References.
-            (progn
-              (goto-char p)
-              (if (search-forward "\nreferences:" nil t)
-                  (progn
-                    (setq end (point))
-                    (prog1
-                        (nnheader-header-value)
-                      (setq ref
-                            (buffer-substring
-                             (progn
-                               (end-of-line)
-                               (search-backward ">" end t)
-                               (1+ (point)))
-                             (progn
-                               (search-backward "<" end t)
-                               (point))))))
-                ;; Get the references from the in-reply-to header if there
-                ;; were no references and the in-reply-to header looks
-                ;; promising.
-                (if (and (search-forward "\nin-reply-to:" nil t)
-                         (setq in-reply-to (nnheader-header-value))
-                         (string-match "<[^>]+>" in-reply-to))
-                    (let (ref2)
-                      (setq ref (substring in-reply-to (match-beginning 0)
-                                           (match-end 0)))
-                      (while (string-match "<[^>]+>" in-reply-to (match-end 0))
-                        (setq ref2 (substring in-reply-to (match-beginning 0)
-                                              (match-end 0)))
-                        (when (> (length ref2) (length ref))
-                          (setq ref ref2)))
-                      ref)
-                  (setq ref nil))))
-            ;; Chars.
-            (progn
-              (goto-char p)
-              (if (search-forward "\nchars: " nil t)
-                  (if (numberp (setq chars (ignore-errors (read cur))))
-                      chars -1)
-                -1))
-            ;; Lines.
-            (progn
-              (goto-char p)
-              (if (search-forward "\nlines: " nil t)
-                  (if (numberp (setq lines (ignore-errors (read cur))))
-                      lines -1)
-                -1))
-            ;; Xref.
-            (progn
-              (goto-char p)
-              (and (search-forward "\nxref:" nil t)
-                   (nnheader-header-value)))
-            ;; Extra.
-            (when gnus-extra-headers
-              (let ((extra gnus-extra-headers)
-                    out)
-                (while extra
-                  (goto-char p)
-                  (when (search-forward
-                         (concat "\n" (symbol-name (car extra)) ":") nil t)
-                    (push (cons (car extra) (nnheader-header-value))
-                          out))
-                  (pop extra))
-                out))))
-          (when (equal id ref)
-            (setq ref nil))
-          (when gnus-alter-header-function
-            (funcall gnus-alter-header-function header)
-            (setq id (mail-header-id header)
-                  ref (gnus-parent-id (mail-header-references header))))
          (when (setq header
                      (gnus-dependencies-add-header
                       header dependencies force-new))
-            (push header headers))
+            (push header headers)))
-          (goto-char (point-max))
-          (widen))
        (nreverse headers)))))
 ;; Goes through the xover lines and returns a list of vectors
@@ -8702,7 +8560,8 @@ SCORE."
 When called interactively, ID is the Message-ID of the current
 article.  If thread-only is non-nil limit the summary buffer to
 these articles."
-  (interactive (list (mail-header-id (gnus-summary-article-header))))
+  (interactive (list (mail-header-id (gnus-summary-article-header))
+                     current-prefix-arg))
  (let ((articles (gnus-articles-in-thread
                   (gnus-id-to-thread (gnus-root-id id))))
        ;;we REALLY want the whole thread---this prevents cut-threads
@@ -9125,13 +8984,13 @@ Return the number of articles fetched."
    result))
 (defun gnus-summary-refer-thread (&optional limit)
-  "Fetch all articles in the current thread.  For backends
+  "Fetch all articles in the current thread. For backends that
-that know how to search for threads (currently only 'nnimap)
+know how to search for threads (currently only 'nnimap) a
-a non-numeric prefix arg will use nnir to search the entire
+non-numeric prefix arg will search the entire
 server; without a prefix arg only the current group is
-searched.  If the variable `gnus-refer-thread-use-nnir' is
+searched. If the variable `gnus-refer-thread-use-search' is
-non-nil the prefix arg has the reverse meaning.  If no
+non-nil the prefix arg has the reverse meaning. If no
-backend-specific `request-thread' function is available fetch
+backend-specific 'request-thread function is available fetch
 LIMIT (the numerical prefix) old headers.  If LIMIT is
 non-numeric or nil fetch the number specified by the
 `gnus-refer-thread-limit' variable."
@@ -9141,9 +9000,9 @@ non-numeric or nil fetch the number specified by the
         (gnus-inhibit-demon t)
         (gnus-summary-ignore-duplicates t)
         (gnus-read-all-available-headers t)
-         (gnus-refer-thread-use-nnir
+         (gnus-refer-thread-use-search
          (if (and (not (null limit)) (listp limit))
-              (not gnus-refer-thread-use-nnir) gnus-refer-thread-use-nnir))
+              (not gnus-refer-thread-use-search) gnus-refer-thread-use-search))
         (new-headers
          (if (gnus-check-backend-function
               'request-thread gnus-newsgroup-name)
@@ -9284,9 +9143,9 @@ non-numeric or nil fetch the number specified by the
      (dolist (method gnus-refer-article-method)
        (push (if (eq 'current method)
                  gnus-current-select-method
-                (if (eq 'nnir (car method))
+                (if (eq 'nnselect (car method))
                    (list
-                     'nnir
+                     'nnselect
                     (or (cadr method)
                         (gnus-method-to-server gnus-current-select-method)))
                  method))
diff --git a/lisp/gnus/gnus.el b/lisp/gnus/gnus.el
index 295395c79c2..4e3fc9868b4 100644
--- a/lisp/gnus/gnus.el
+++ b/lisp/gnus/gnus.el
@@ -1607,7 +1607,7 @@ total number of articles in the group.")
 :variable-default (mapcar
                    (lambda (g) (list g t))
                    '("delayed$" "drafts$" "queue$" "INBOX$"
-                      "^nnmairix:" "^nnir:" "archive"))
+                      "^nnmairix:" "^nnselect:" "archive"))
 :variable-document
 "Groups in which the registry should be turned off."
 :variable-group gnus-registry
@@ -3153,7 +3153,10 @@ that that variable is buffer-local to the summary buffers."
 (defun gnus-kill-ephemeral-group (group)
  "Remove ephemeral GROUP from relevant structures."
-  (remhash group gnus-newsrc-hashtb))
+  (remhash group gnus-newsrc-hashtb)
+    (setq gnus-newsrc-alist
+        (delq (assoc group gnus-newsrc-alist)
+              gnus-newsrc-alist)))
 (defun gnus-simplify-mode-line ()
  "Make mode lines a bit simpler."
diff --git a/lisp/gnus/nndiary.el b/lisp/gnus/nndiary.el
index 945ef0351e5..7894285bdf3 100644
--- a/lisp/gnus/nndiary.el
+++ b/lisp/gnus/nndiary.el
@@ -992,7 +992,7 @@ all.  This may very well take some time.")
        (narrow-to-region
         (goto-char (point-min))
         (if (search-forward "\n\n" nil t) (1- (point)) (point-max))))
-      (let ((headers (nnheader-parse-naked-head)))
+      (let ((headers (nnheader-parse-head t)))
        (setf (mail-header-chars  headers) chars)
        (setf (mail-header-number headers) number)
        headers))))
diff --git a/lisp/gnus/nnfolder.el b/lisp/gnus/nnfolder.el
index c27af1742d8..6ff99056d84 100644
--- a/lisp/gnus/nnfolder.el
+++ b/lisp/gnus/nnfolder.el
@@ -1160,7 +1160,7 @@ This command does not work if you use short group names."
        (if (search-forward "\n\n" e t) (setq e (1- (point)))))
      (with-temp-buffer
        (insert-buffer-substring buf b e)
-        (let ((headers (nnheader-parse-naked-head)))
+        (let ((headers (nnheader-parse-head t)))
          (setf (mail-header-chars  headers) chars)
          (setf (mail-header-number headers) number)
          headers)))))
diff --git a/lisp/gnus/nnheader.el b/lisp/gnus/nnheader.el
index fee7a169ff9..1a50697bf5d 100644
--- a/lisp/gnus/nnheader.el
+++ b/lisp/gnus/nnheader.el
@@ -28,6 +28,10 @@
 (eval-when-compile (require 'cl-lib))
+(defvar gnus-decode-encoded-word-function)
+(defvar gnus-decode-encoded-address-function)
+(defvar gnus-alter-header-function)
 (defvar nnmail-extra-headers)
 (defvar gnus-newsgroup-name)
 (defvar jka-compr-compression-info-list)
@@ -39,6 +43,7 @@
 (require 'mail-utils)
 (require 'mm-util)
 (require 'gnus-util)
+(autoload 'gnus-remove-odd-characters "gnus-sum")
 (autoload 'gnus-range-add "gnus-range")
 (autoload 'gnus-remove-from-range "gnus-range")
 ;; FIXME none of these are used explicitly in this file.
@@ -188,124 +193,167 @@ on your system, you could say something like:
 (autoload 'ietf-drums-unfold-fws "ietf-drums")
-(defun nnheader-parse-naked-head (&optional number)
-  ;; This function unfolds continuation lines in this buffer
+(defsubst nnheader-head-make-header (number)
-  ;; destructively.  When this side effect is unwanted, use
+  "Using data of type 'head in the current buffer
-  ;; `nnheader-parse-head' instead of this function.
+  return a full mail header with article NUMBER."
-  (let ((case-fold-search t)
+  (let ((p (point-min))
-        (buffer-read-only nil)
        (cur (current-buffer))
-        (p (point-min))
+        in-reply-to chars lines end ref)
-        in-reply-to lines ref)
+    ;; This implementation of this function, with nine
-    (nnheader-remove-cr-followed-by-lf)
+    ;; search-forwards instead of the one re-search-forward and a
-    (ietf-drums-unfold-fws)
+    ;; case (which basically was the old function) is actually
-    (subst-char-in-region (point-min) (point-max) ?\t ? )
+    ;; about twice as fast, even though it looks messier.  You
-    (goto-char p)
+    ;; can't have everything, I guess.  Speed and elegance don't
-    (insert "\n")
+    ;; always go hand in hand.
-    (prog1
+    (make-full-mail-header
-        ;; This implementation of this function, with nine
+     ;; Number.
-        ;; search-forwards instead of the one re-search-forward and a
+     number
-        ;; case (which basically was the old function) is actually
+     ;; Subject.
-        ;; about twice as fast, even though it looks messier.  You
+     (progn
-        ;; can't have everything, I guess.  Speed and elegance don't
+       (goto-char p)
-        ;; always go hand in hand.
+       (if (search-forward "\nsubject:" nil t)
-        (make-full-mail-header
+           (funcall gnus-decode-encoded-word-function
-         ;; Number.
+                    (nnheader-header-value))
-         (or number 0)
+         "(none)"))
-         ;; Subject.
+     ;; From.
-         (progn
+     (progn
-           (goto-char p)
+       (goto-char p)
-           (if (search-forward "\nsubject:" nil t)
+       (if (search-forward "\nfrom:" nil t)
-               (nnheader-header-value) "(none)"))
+           (funcall gnus-decode-encoded-address-function
-         ;; From.
+                    (nnheader-header-value))
-         (progn
+         "(nobody)"))
-           (goto-char p)
+     ;; Date.
-           (if (search-forward "\nfrom:" nil t)
+     (progn
-               (nnheader-header-value) "(nobody)"))
+       (goto-char p)
-         ;; Date.
+       (if (search-forward "\ndate:" nil t)
-         (progn
+           (nnheader-header-value) ""))
-           (goto-char p)
+     ;; Message-ID.
-           (if (search-forward "\ndate:" nil t)
+     (progn
-               (nnheader-header-value) ""))
+       (goto-char p)
-         ;; Message-ID.
+       (if (re-search-forward
-         (progn
+            "^message-id: *\\(<[^\n\t> ]+>\\)" nil t)
-           (goto-char p)
+           ;; We do it this way to make sure the Message-ID
-           (if (search-forward "\nmessage-id:" nil t)
+           ;; is (somewhat) syntactically valid.
-               (buffer-substring
+           (buffer-substring (match-beginning 1)
-                (1- (or (search-forward "<" (point-at-eol) t)
+                             (match-end 1))
-                        (point)))
+         ;; If there was no message-id, we just fake one to make
-                (or (search-forward ">" (point-at-eol) t) (point)))
+         ;; subsequent routines simpler.
-             ;; If there was no message-id, we just fake one to make
+         (nnheader-generate-fake-message-id number)))
-             ;; subsequent routines simpler.
+     ;; References.
-             (nnheader-generate-fake-message-id number)))
+     (progn
-         ;; References.
+       (goto-char p)
-         (progn
+       (if (search-forward "\nreferences:" nil t)
+           (progn
+             (setq end (point))
+             (prog1
+                 (nnheader-header-value)
+               (setq ref
+                     (buffer-substring
+                      (progn
+                        (end-of-line)
+                        (search-backward ">" end t)
+                        (1+ (point)))
+                      (progn
+                        (search-backward "<" end t)
+                        (point))))))
+         ;; Get the references from the in-reply-to header if there
+         ;; were no references and the in-reply-to header looks
+         ;; promising.
+         (if (and (search-forward "\nin-reply-to:" nil t)
+                  (setq in-reply-to (nnheader-header-value))
+                  (string-match "<[^>]+>" in-reply-to))
+             (let (ref2)
+               (setq ref (substring in-reply-to (match-beginning 0)
+                                    (match-end 0)))
+               (while (string-match "<[^>]+>" in-reply-to (match-end 0))
+                 (setq ref2 (substring in-reply-to (match-beginning 0)
+                                       (match-end 0)))
+                 (when (> (length ref2) (length ref))
+                   (setq ref ref2)))
+               ref)
+           nil)))
+     ;; Chars.
+     (progn
+       (goto-char p)
+       (if (search-forward "\nchars: " nil t)
+           (if (numberp (setq chars (ignore-errors (read cur))))
+               chars -1)
+         -1))
+     ;; Lines.
+     (progn
+       (goto-char p)
+       (if (search-forward "\nlines: " nil t)
+           (if (numberp (setq lines (ignore-errors (read cur))))
+               lines -1)
+         -1))
+     ;; Xref.
+     (progn
+       (goto-char p)
+       (and (search-forward "\nxref:" nil t)
+            (nnheader-header-value)))
+     ;; Extra.
+     (when nnmail-extra-headers
+       (let ((extra nnmail-extra-headers)
+             out)
+         (while extra
           (goto-char p)
-           (if (search-forward "\nreferences:" nil t)
+           (when (search-forward
-               (nnheader-header-value)
+                  (concat "\n" (symbol-name (car extra)) ":") nil t)
-             ;; Get the references from the in-reply-to header if
+             (push (cons (car extra) (nnheader-header-value))
-             ;; there were no references and the in-reply-to header
+                   out))
-             ;; looks promising.
+           (pop extra))
-             (if (and (search-forward "\nin-reply-to:" nil t)
+         out)))))
-                      (setq in-reply-to (nnheader-header-value))
-                      (string-match "<[^\n>]+>" in-reply-to))
+(defun nnheader-parse-head (&optional naked temp)
-                 (let (ref2)
+  "Parse data of type 'header in the current buffer and return a
-                   (setq ref (substring in-reply-to (match-beginning 0)
+  mail header, modifying the buffer contents in the process. The
-                                        (match-end 0)))
+  buffer is assumed to begin each header with an \"Article
-                   (while (string-match "<[^\n>]+>"
+  retrieved\" line with an article number; If NAKED is non-nil
-                                        in-reply-to (match-end 0))
+  this line is assumed absent, and the buffer should contain a
-                     (setq ref2 (substring in-reply-to (match-beginning 0)
+  single header's worth of data. If TEMP is non-nil the data is
-                                           (match-end 0)))
+  first copied to a temporary buffer leaving the original buffer
-                     (when (> (length ref2) (length ref))
+  untouched."
-                       (setq ref ref2)))
+  (let ((cur (current-buffer))
-                   ref)
+        (num 0)
-               nil)))
+        (beg (point-min))
-         ;; Chars.
+        (end (point-max))
-         0
+        buf)
-         ;; Lines.
+    (when (or naked
-         (progn
+              ;; Search to the beginning of the next header.  Error
-           (goto-char p)
+              ;; messages do not begin with 2 or 3.
-           (if (search-forward "\nlines: " nil t)
+              (when (re-search-forward "^[23][0-9]+ " nil t)
-               (if (numberp (setq lines (read cur)))
+                (setq num (read cur)
-                   lines 0)
+                      beg (point)
-             0))
+                      end (if (search-forward "\n.\n" nil t)
-         ;; Xref.
+                              (goto-char  (- (point) 2))
-         (progn
+                            (point)))))
-           (goto-char p)
+      ;; When TEMP copy the data to a temporary buffer
-           (and (search-forward "\nxref:" nil t)
+      (if temp
-                (nnheader-header-value)))
+          (progn
-         ;; Extra.
+            (set-buffer (setq buf (generate-new-buffer " *nnheader-temp*")))
-         (when nnmail-extra-headers
+            (insert-buffer-substring cur beg end))
-           (let ((extra nnmail-extra-headers)
+        ;; Otherwise just narrow to the data
-                 out)
+        (narrow-to-region beg end))
-             (while extra
+      (let ((case-fold-search t)
-               (goto-char p)
+            (buffer-read-only nil)
-               (when (search-forward
+            header)
-                      (concat "\n" (symbol-name (car extra)) ":") nil t)
+        (nnheader-remove-cr-followed-by-lf)
-                 (push (cons (car extra) (nnheader-header-value))
+        (ietf-drums-unfold-fws)
-                       out))
+        (subst-char-in-region (point-min) (point-max) ?\t ?  t)
-               (pop extra))
+        (subst-char-in-region (point-min) (point-max) ?\r ?  t)
-             out)))
+        (goto-char (point-min))
-      (goto-char p)
+        (insert "\n")
-      (delete-char 1))))
+        (setq header (nnheader-head-make-header num))
+        (goto-char (point-min))
-(defun nnheader-parse-head (&optional naked)
+        (delete-char 1)
-  (let ((cur (current-buffer)) num beg end)
+        (if temp
-    (when (if naked
+            (kill-buffer buf)
-              (setq num 0
+          (goto-char (point-max))
-                    beg (point-min)
+          (widen))
-                    end (point-max))
+        (when gnus-alter-header-function
-            ;; Search to the beginning of the next header.  Error
+          (funcall gnus-alter-header-function header))
-            ;; messages do not begin with 2 or 3.
+        header))))
-            (when (re-search-forward "^[23][0-9]+ " nil t)
-              (setq num (read cur)
-                    beg (point)
-                    end (if (search-forward "\n.\n" nil t)
-                            (goto-char  (- (point) 2))
-                          (point)))))
-      (with-temp-buffer
-        (insert-buffer-substring cur beg end)
-        (nnheader-parse-naked-head num)))))
 (defmacro nnheader-nov-skip-field ()
  '(search-forward "\t" eol 'move))
@@ -347,24 +395,43 @@ on your system, you could say something like:
            'id)
       (nnheader-generate-fake-message-id ,number))))
-(defun nnheader-parse-nov ()
+(defalias 'nnheader-nov-make-header 'nnheader-parse-nov)
+(autoload 'gnus-extract-message-id-from-in-reply-to "gnus-sum")
+(defun nnheader-parse-nov (&optional number)
  (let ((eol (point-at-eol))
-        (number (nnheader-nov-read-integer)))
+        references in-reply-to x header)
-    (vector
+      (setq header
-     number                             ; number
+            (make-full-mail-header
-     (nnheader-nov-field)               ; subject
+             (or number (nnheader-nov-read-integer))      ; number
-     (nnheader-nov-field)               ; from
+             (condition-case () ; subject
-     (nnheader-nov-field)               ; date
+                 (gnus-remove-odd-characters
-     (nnheader-nov-read-message-id number) ; id
+                  (funcall gnus-decode-encoded-word-function
-     (nnheader-nov-field)               ; refs
+                           (setq x (nnheader-nov-field))))
-     (nnheader-nov-read-integer)        ; chars
+               (error x))
-     (nnheader-nov-read-integer)        ; lines
+             (condition-case () ; from
-     (if (eq (char-after) ?\n)
+                 (gnus-remove-odd-characters
-         nil
+                  (funcall gnus-decode-encoded-address-function
-       (if (looking-at "Xref: ")
+                           (setq x (nnheader-nov-field))))
-           (goto-char (match-end 0)))
+               (error x))
-       (nnheader-nov-field))            ; Xref
+             (nnheader-nov-field)       ; date
-     (nnheader-nov-parse-extra))))      ; extra
+             (nnheader-nov-read-message-id number)      ; id
+             (setq references (nnheader-nov-field))     ; refs
+             (nnheader-nov-read-integer) ; chars
+             (nnheader-nov-read-integer) ; lines
+             (unless (eobp)
+               (if (looking-at "Xref: ")
+                   (goto-char (match-end 0)))
+               (nnheader-nov-field)) ; Xref
+             (nnheader-nov-parse-extra))) ; extra
+      (when (and (string= references "")
+                 (setq in-reply-to (mail-header-extra header))
+                 (setq in-reply-to (cdr (assq 'In-Reply-To in-reply-to))))
+        (setf (mail-header-references header)
+              (gnus-extract-message-id-from-in-reply-to in-reply-to)))
+      header))
 (defun nnheader-insert-nov (header)
  (princ (mail-header-number header) (current-buffer))
@@ -399,17 +466,6 @@ on your system, you could say something like:
      (delete-char 1))
    (forward-line 1)))
-(defun nnheader-parse-overview-file (file)
-  "Parse FILE and return a list of headers."
-  (mm-with-unibyte-buffer
-    (nnheader-insert-file-contents file)
-    (goto-char (point-min))
-    (let (headers)
-      (while (not (eobp))
-        (push (nnheader-parse-nov) headers)
-        (forward-line 1))
-      (nreverse headers))))
 (defun nnheader-write-overview-file (file headers)
  "Write HEADERS to FILE."
  (with-temp-file file
diff --git a/lisp/gnus/nnimap.el b/lisp/gnus/nnimap.el
index 507e12a55e7..d797e893f51 100644
--- a/lisp/gnus/nnimap.el
+++ b/lisp/gnus/nnimap.el
@@ -1686,7 +1686,7 @@ If LIMIT, first try to limit the search to the N last articles."
        (gnus-add-to-range
         (gnus-add-to-range
          (gnus-range-add (gnus-info-read info)
-                          vanished)
+                          vanished)
          (cdr (assq '%Flagged flags)))
         (cdr (assq '%Seen flags))))
  (let ((marks (gnus-info-marks info)))
@@ -1851,15 +1851,15 @@ If LIMIT, first try to limit the search to the N last articles."
  (setq nnimap-status-string "Read-only server")
  nil)
-(defvar gnus-refer-thread-use-nnir) ;; gnus-sum.el
+(defvar gnus-refer-thread-use-search) ;; gnus-sum.el
 (declare-function gnus-fetch-headers "gnus-sum"
                  (articles &optional limit force-new dependencies))
-(autoload 'nnir-search-thread "nnir")
+(autoload 'nnselect-search-thread "nnselect")
 (deffoo nnimap-request-thread (header &optional group server)
-  (if gnus-refer-thread-use-nnir
+  (if gnus-refer-thread-use-search
-      (nnir-search-thread header)
+      (nnselect-search-thread header)
    (when (nnimap-change-group group server)
      (let* ((cmd (nnimap-make-thread-query header))
             (result (with-current-buffer (nnimap-buffer)
diff --git a/lisp/gnus/nnir.el b/lisp/gnus/nnir.el
index 722969c21ba..2ec39cf34c9 100644
--- a/lisp/gnus/nnir.el
+++ b/lisp/gnus/nnir.el
@@ -10,6 +10,7 @@
 ;; IMAP search improved by Daniel Pittman  <daniel@rimspace.net>.
 ;; nnmaildir support for Swish++ and Namazu backends by:
 ;;   Justus Piater <Justus <at> Piater.name>
+;; Mostly rewritten by Andrew Cohen <cohen@bu.edu> from 2010
 ;; Keywords: news mail searching ir
 ;; This file is part of GNU Emacs.
@@ -29,20 +30,11 @@
 ;;; Commentary:
-;; What does it do?  Well, it allows you to search your mail using
+;; What does it do?  Well, it searches your mail using some search
-;; some search engine (imap, namazu, swish-e and others -- see
+;; engine (imap, namazu, swish-e, gmane and others -- see later).
-;; later) by typing `G G' in the Group buffer.  You will then get a
-;; buffer which shows all articles matching the query, sorted by
-;; Retrieval Status Value (score).
-;; When looking at the retrieval result (in the Summary buffer) you
-;; can type `A W' (aka M-x gnus-warp-to-article RET) on an article.  You
-;; will be warped into the group this article came from. Typing `A T'
-;; (aka M-x gnus-summary-refer-thread RET) will warp to the group and
-;; also show the thread this article is part of.
 ;; The Lisp setup may involve setting a few variables and setting up the
-;; search engine. You can define the variables in the server definition
+;; search engine.  You can define the variables in the server definition
 ;; like this :
 ;;   (setq gnus-secondary-select-methods '(
 ;;       (nnimap "" (nnimap-address "localhost")
@@ -53,6 +45,45 @@
 ;; an alist, type `C-h v nnir-engines RET' for more information; this
 ;; includes examples for setting `nnir-search-engine', too.)
+;; The entry to searching is the single function `nnir-run-query',
+;; which dispatches the search to the proper search function.  The
+;; argument of `nnir-run-query' is an alist with two keys:
+;; 'nnir-query-spec and 'nnir-group-spec.  The value for
+;; 'nnir-query-spec is an alist.  The only required key/value pair is
+;; (query . "query") specifying the search string to pass to the query
+;; engine.  Individual engines may have other elements.  The value of
+;; 'nnir-group-spec is a list with the specification of the
+;; groups/servers to search.  The format of the 'nnir-group-spec is
+;; (("server1" ("group11" "group12")) ("server2" ("group21"
+;; "group22"))). If any of the group lists is absent then all groups
+;; on that server are searched.
+;; The output of `nnir-run-query' is a vector, each element of which
+;; should in turn be a three-element vector with the form: [fully
+;; prefixed group-name of the article; the article number; the
+;; Retrieval Status Value (RSV)] as returned from the search engine.
+;; An RSV is the score assigned to the document by the search engine.
+;; For Boolean search engines, the RSV is always 1000 (or 1 or 100, or
+;; whatever you like).
+;; A vector of this form is used by the nnselect backend to create
+;; virtual groups.  So nnir-run-query is a suitable function to use in
+;; nnselect groups.
+;; The default sorting order of articles in an nnselect summary buffer
+;; is based on the order of the articles in the above mentioned
+;; vector, so that's where you can do the sorting you'd like.  Maybe
+;; it would be nice to have a way of displaying the search result
+;; sorted differently?
+;; So what do you need to do when you want to add another search
+;; engine?  You write a function that executes the query.  Temporary
+;; data from the search engine can be put in `nnir-tmp-buffer'.  This
+;; function should return the list of articles as a vector, as
+;; described above.  Then, you need to register this backend in
+;; `nnir-engines'.  Then, users can choose the backend by setting
+;; `nnir-search-engine' as a server variable.
 ;; If you use one of the local indices (namazu, find-grep, swish) you
 ;; must also set up a search engine backend.
@@ -75,13 +106,13 @@
 ;; ,----
 ;; | package conf;  # Don't remove this line!
 ;; |
-;; | # Paths which will not be indexed. Don't use `^' or `$' anchors.
+;; | # Paths which will not be indexed.  Don't use `^' or `$' anchors.
 ;; | $EXCLUDE_PATH = "spam|sent";
 ;; |
-;; | # Header fields which should be searchable. case-insensitive
+;; | # Header fields which should be searchable.  case-insensitive
 ;; | $REMAIN_HEADER = "from|date|message-id|subject";
 ;; |
-;; | # Searchable fields. case-insensitive
+;; | # Searchable fields.  case-insensitive
 ;; | $SEARCH_FIELD = "from|date|message-id|subject";
 ;; |
 ;; | # The max length of a word.
@@ -121,72 +152,17 @@
 ;; |          (nnml-active-file "~/News/cache/active"))
 ;; `----
-;; Developer information:
-;; I have tried to make the code expandable.  Basically, it is divided
-;; into two layers.  The upper layer is somewhat like the `nnvirtual'
-;; backend: given a specification of what articles to show from
-;; another backend, it creates a group containing exactly those
-;; articles.  The lower layer issues a query to a search engine and
-;; produces such a specification of what articles to show from the
-;; other backend.
-;; The interface between the two layers consists of the single
-;; function `nnir-run-query', which dispatches the search to the
-;; proper search function.  The argument of `nnir-run-query' is an
-;; alist with two keys: 'nnir-query-spec and 'nnir-group-spec. The
-;; value for 'nnir-query-spec is an alist. The only required key/value
-;; pair is (query . "query") specifying the search string to pass to
-;; the query engine. Individual engines may have other elements. The
-;; value of 'nnir-group-spec is a list with the specification of the
-;; groups/servers to search.  The format of the 'nnir-group-spec is
-;; (("server1" ("group11" "group12")) ("server2" ("group21"
-;; "group22"))). If any of the group lists is absent then all groups
-;; on that server are searched.
-;; The output of `nnir-run-query' is supposed to be a vector, each
-;; element of which should in turn be a three-element vector.  The
-;; first element should be full group name of the article, the second
-;; element should be the article number, and the third element should
-;; be the Retrieval Status Value (RSV) as returned from the search
-;; engine.  An RSV is the score assigned to the document by the search
-;; engine.  For Boolean search engines, the RSV is always 1000 (or 1
-;; or 100, or whatever you like).
-;; The sorting order of the articles in the summary buffer created by
-;; nnir is based on the order of the articles in the above mentioned
-;; vector, so that's where you can do the sorting you'd like.  Maybe
-;; it would be nice to have a way of displaying the search result
-;; sorted differently?
-;; So what do you need to do when you want to add another search
-;; engine?  You write a function that executes the query.  Temporary
-;; data from the search engine can be put in `nnir-tmp-buffer'.  This
-;; function should return the list of articles as a vector, as
-;; described above.  Then, you need to register this backend in
-;; `nnir-engines'.  Then, users can choose the backend by setting
-;; `nnir-search-engine' as a server variable.
 ;;; Code:
 ;;; Setup:
-(require 'nnoo)
-(require 'gnus-group)
-(require 'message)
-(require 'gnus-util)
 (eval-when-compile (require 'cl-lib))
+(require 'gnus)
 ;;; Internal Variables:
-(defvar nnir-memo-query nil
+(defvar gnus-inhibit-demon)
-  "Internal: stores current query.")
-(defvar nnir-memo-server nil
-  "Internal: stores current server.")
-(defvar nnir-artlist nil
-  "Internal: stores search result.")
 (defvar nnir-search-history ()
  "Internal: the history for querying search options in nnir.")
@@ -203,30 +179,19 @@
    ("to" . "TO")
    ("from" . "FROM")
    ("body" . "BODY")
-    ("imap" . ""))
+    ("imap" . "")
+    ("gmail" . "X-GM-RAW"))
  "Mapping from user readable keys to IMAP search items for use in nnir.")
 (defvar nnir-imap-search-other "HEADER %S"
-  "The IMAP search item to use for anything other than
+  "The IMAP search item for anything other than `nnir-imap-search-arguments'.
-`nnir-imap-search-arguments'.  By default this is the name of an
+By default this is the name of an email header field.")
-email header field.")
 (defvar nnir-imap-search-argument-history ()
  "The history for querying search options in nnir.")
 ;;; Helper macros
-;; Data type article list.
-(defmacro nnir-artlist-length (artlist)
-  "Return number of articles in artlist."
-  `(length ,artlist))
-(defmacro nnir-artlist-article (artlist n)
-  "Return from ARTLIST the Nth artitem (counting starting at 1)."
-  `(when (> ,n 0)
-     (elt ,artlist (1- ,n))))
 (defmacro nnir-artitem-group (artitem)
  "Return the group from the ARTITEM."
  `(elt ,artitem 0))
@@ -239,52 +204,6 @@ email header field.")
  "Return the Retrieval Status Value (RSV, score) from the ARTITEM."
  `(elt ,artitem 2))
-(defmacro nnir-article-group (article)
-  "Return the group for ARTICLE."
-  `(nnir-artitem-group (nnir-artlist-article nnir-artlist ,article)))
-(defmacro nnir-article-number (article)
-  "Return the number for ARTICLE."
-  `(nnir-artitem-number (nnir-artlist-article nnir-artlist ,article)))
-(defmacro nnir-article-rsv (article)
-  "Return the rsv for ARTICLE."
-  `(nnir-artitem-rsv (nnir-artlist-article nnir-artlist ,article)))
-(defsubst nnir-article-ids (article)
-  "Return the pair `(nnir id . real id)' of ARTICLE."
-  (cons article (nnir-article-number article)))
-(defmacro nnir-categorize (sequence keyfunc &optional valuefunc)
-  "Sort a SEQUENCE into categories and returns a list of the form
-`((key1 (element11 element12)) (key2 (element21 element22))'.
-The category key for a member of the sequence is obtained
-as `(KEYFUNC member)' and the corresponding element is just
-`member'.  If VALUEFUNC is non-nil, the element of the list
-is `(VALUEFUNC member)'."
-  `(unless (null ,sequence)
-     (let (value)
-       (mapc
-        (lambda (member)
-          (let ((y (,keyfunc member))
-                (x ,(if valuefunc
-                        `(,valuefunc member)
-                      'member)))
-            (if (assoc y value)
-                (push x (cadr (assoc y value)))
-              (push (list y (list x)) value))))
-        ,sequence)
-       value)))
-;;; Finish setup:
-(require 'gnus-sum)
-(nnoo-declare nnir)
-(nnoo-define-basics nnir)
-(gnus-declare-backend "nnir" 'mail 'virtual)
 ;;; User Customizable Variables:
@@ -293,43 +212,17 @@ is `(VALUEFUNC member)'."
  :group 'gnus)
 (defcustom nnir-ignored-newsgroups ""
-  "A regexp to match newsgroups in the active file that should
+  "Newsgroups to skip when searching.
-be skipped when searching."
+Any newsgroup in the active file matching this regexp will be
+skipped when searching."
  :version "24.1"
  :type '(regexp)
  :group 'nnir)
-(defcustom nnir-summary-line-format nil
-  "The format specification of the lines in an nnir summary buffer.
-All the items from `gnus-summary-line-format' are available, along
-with three items unique to nnir summary buffers:
-%Z    Search retrieval score value (integer)
-%G    Article original full group name (string)
-%g    Article original short group name (string)
-If nil this will use `gnus-summary-line-format'."
-  :version "24.1"
-  :type '(choice (const :tag "gnus-summary-line-format" nil) string)
-  :group 'nnir)
-(defcustom nnir-retrieve-headers-override-function nil
-  "If non-nil, a function that accepts an article list and group
-and populates the `nntp-server-buffer' with the retrieved
-headers.  Must return either `nov' or `headers' indicating the
-retrieved header format.
-If this variable is nil, or if the provided function returns nil for
-a search result, `gnus-retrieve-headers' will be called instead."
-  :version "24.1"
-  :type '(choice (const :tag "gnus-retrieve-headers" nil) function)
-  :group 'nnir)
 (defcustom nnir-imap-default-search-key "whole message"
-  "The default IMAP search key for an nnir search.  Must be one of
+  "The default IMAP search key for an nnir search.
-the keys in `nnir-imap-search-arguments'.  To use raw imap queries
+Must be one of the keys in `nnir-imap-search-arguments'.  To use
-by default set this to \"imap\"."
+raw imap queries by default set this to \"imap\"."
  :version "24.1"
  :type `(choice ,@(mapcar (lambda (elem) (list 'const (car elem)))
                           nnir-imap-search-arguments))
@@ -357,9 +250,9 @@ Instead, use this:
  :group 'nnir)
 (defcustom nnir-swish++-remove-prefix (concat (getenv "HOME") "/Mail/")
-  "The prefix to remove from each file name returned by swish++
+  "The prefix to remove from swish++ file names to get group names.
-in order to get a group name (albeit with / instead of .).  This is a
+Resulting names have '/' in place of '.'.  This is a regular
-regular expression.
+expression.
 This variable is very similar to `nnir-namazu-remove-prefix', except
 that it is for swish++, not Namazu."
@@ -408,9 +301,9 @@ This could be a server parameter."
  :group 'nnir)
 (defcustom nnir-swish-e-remove-prefix (concat (getenv "HOME") "/Mail/")
-  "The prefix to remove from each file name returned by swish-e
+  "The prefix to remove from swish-e file names to get group names.
-in order to get a group name (albeit with / instead of .).  This is a
+Resulting names have '/' in place of '.'.  This is a regular
-regular expression.
+expression.
 This variable is very similar to `nnir-namazu-remove-prefix', except
 that it is for swish-e, not Namazu.
@@ -441,8 +334,8 @@ Instead, use this:
  :group 'nnir)
 (defcustom nnir-hyrex-remove-prefix (concat (getenv "HOME") "/Mail/")
-  "The prefix to remove from each file name returned by HyREX
+  "The prefix to remove from HyREX file names to get group names.
-in order to get a group name (albeit with / instead of .).
+Restulting names have '/' in place  of '.'.
 For example, suppose that HyREX returns file names such as
 \"/home/john/Mail/mail/misc/42\".  For this example, use the following
@@ -478,8 +371,8 @@ Instead, use this:
  :group 'nnir)
 (defcustom nnir-namazu-remove-prefix (concat (getenv "HOME") "/Mail/")
-  "The prefix to remove from each file name returned by Namazu
+  "The prefix to remove from Namazu file names to get group names.
-in order to get a group name (albeit with / instead of .).
+Resulting names have '/' in place of '.'.
 For example, suppose that Namazu returns file names such as
 \"/home/john/Mail/mail/misc/42\".  For this example, use the following
@@ -509,9 +402,9 @@ Instead, use this:
 (defcustom nnir-notmuch-remove-prefix
  (regexp-quote (or (getenv "MAILDIR") (expand-file-name "~/Mail")))
-  "The prefix to remove from each file name returned by notmuch
+  "The prefix to remove from notmuch file names to get group names.
-in order to get a group name (albeit with / instead of .).  This is a
+Resulting names have '/' in place of '.'.  This is a regular
-regular expression.
+expression.
 This variable is very similar to `nnir-namazu-remove-prefix', except
 that it is for notmuch, not Namazu."
@@ -590,347 +483,12 @@ Add an entry here when adding a new search engine.")
                        ,@(mapcar (lambda (elem) (list 'const (car elem)))
                                  nnir-engines)))))
-;; Gnus glue.
-(declare-function gnus-group-topic-name "gnus-topic" ())
-(declare-function gnus-topic-find-groups "gnus-topic"
-                  (topic &optional level all lowest recursive))
-(defun gnus-group-make-nnir-group (nnir-extra-parms &optional specs)
-  "Create an nnir group.
-Prompt for a search query and determine the groups to search as
-follows: if called from the *Server* buffer search all groups
-belonging to the server on the current line; if called from the
-*Group* buffer search any marked groups, or the group on the current
-line, or all the groups under the current topic.  Calling with a
-prefix-arg prompts for additional search-engine specific constraints.
-A non-nil `specs' arg must be an alist with `nnir-query-spec' and
-`nnir-group-spec' keys, and skips all prompting."
-  (interactive "P")
-  (let* ((group-spec
-          (or (cdr (assq 'nnir-group-spec specs))
-            (if (gnus-server-server-name)
-                (list (list (gnus-server-server-name)))
-              (nnir-categorize
-               (or gnus-group-marked
-                   (if (gnus-group-group-name)
-                       (list (gnus-group-group-name))
-                     (mapcar (lambda (entry)
-                               (gnus-info-group (cadr entry)))
-                             (gnus-topic-find-groups (gnus-group-topic-name)
-                                                     nil t nil t))))
-               gnus-group-server))))
-         (query-spec
-          (or (cdr (assq 'nnir-query-spec specs))
-            (apply
-             'append
-             (list (cons 'query
-                         (read-string "Query: " nil 'nnir-search-history)))
-             (when nnir-extra-parms
-               (mapcar
-                (lambda (x)
-                  (nnir-read-parms (nnir-server-to-search-engine (car x))))
-                group-spec))))))
-    (gnus-group-read-ephemeral-group
-     (concat "nnir-" (message-unique-id))
-     (list 'nnir "nnir")
-     nil
-;     (cons (current-buffer) gnus-current-window-configuration)
-     nil
-     nil nil
-     (list
-      (cons 'nnir-specs (list (cons 'nnir-query-spec query-spec)
-                              (cons 'nnir-group-spec group-spec)))
-      (cons 'nnir-artlist nil)))))
-(defun gnus-summary-make-nnir-group (nnir-extra-parms)
-  "Search a group from the summary buffer."
-  (interactive "P")
-  (gnus-warp-to-article)
-  (let ((spec
-         (list
-          (cons 'nnir-group-spec
-                (list (list
-                       (gnus-group-server gnus-newsgroup-name)
-                       (list gnus-newsgroup-name)))))))
-    (gnus-group-make-nnir-group nnir-extra-parms spec)))
-;; Gnus backend interface functions.
-(deffoo nnir-open-server (server &optional definitions)
-  ;; Just set the server variables appropriately.
-  (let ((backend (car (gnus-server-to-method server))))
-    (if backend
-        (nnoo-change-server backend server definitions)
-      (add-hook 'gnus-summary-generate-hook 'nnir-mode)
-      (nnoo-change-server 'nnir server definitions))))
-(deffoo nnir-request-group (group &optional server dont-check _info)
-  (nnir-possibly-change-group group server)
-  (let ((pgroup (gnus-group-guess-full-name-from-command-method group))
-        length)
-    ;; Check for cached search result or run the query and cache the
-    ;; result.
-    (unless (and nnir-artlist dont-check)
-      (gnus-group-set-parameter
-       pgroup 'nnir-artlist
-       (setq nnir-artlist
-             (nnir-run-query
-              (gnus-group-get-parameter pgroup 'nnir-specs t))))
-      (nnir-request-update-info pgroup (gnus-get-info pgroup)))
-    (with-current-buffer nntp-server-buffer
-      (if (zerop (setq length (nnir-artlist-length nnir-artlist)))
-          (progn
-            (nnir-close-group group)
-            (nnheader-report 'nnir "Search produced empty results."))
-        (nnheader-insert "211 %d %d %d %s\n"
-                         length    ; total #
-                         1         ; first #
-                         length    ; last #
-                         group)))) ; group name
-  nnir-artlist)
-(defvar gnus-inhibit-demon)
-(deffoo nnir-retrieve-headers (articles &optional _group _server _fetch-old)
-  (with-current-buffer nntp-server-buffer
-    (let ((gnus-inhibit-demon t)
-          (articles-by-group (nnir-categorize
-                              articles nnir-article-group nnir-article-ids))
-          headers)
-      (while (not (null articles-by-group))
-        (let* ((group-articles (pop articles-by-group))
-               (artgroup (car group-articles))
-               (articleids (cadr group-articles))
-               (artlist (sort (mapcar 'cdr articleids) '<))
-               (server (gnus-group-server artgroup))
-               (gnus-override-method (gnus-server-to-method server))
-               parsefunc)
-          ;; (nnir-possibly-change-group nil server)
-          (erase-buffer)
-          (pcase (setq gnus-headers-retrieved-by
-                       (or
-                        (and
-                         nnir-retrieve-headers-override-function
-                         (funcall nnir-retrieve-headers-override-function
-                                  artlist artgroup))
-                        (gnus-retrieve-headers artlist artgroup nil)))
-            ('nov
-             (setq parsefunc 'nnheader-parse-nov))
-            ('headers
-             (setq parsefunc 'nnheader-parse-head))
-            (_ (error "Unknown header type %s while requesting articles \
-                    of group %s" gnus-headers-retrieved-by artgroup)))
-          (goto-char (point-min))
-          (while (not (eobp))
-            (let* ((novitem (funcall parsefunc))
-                   (artno (and novitem
-                               (mail-header-number novitem)))
-                   (art (car (rassq artno articleids))))
-              (when art
-                (setf (mail-header-number novitem) art)
-                (push novitem headers))
-              (forward-line 1)))))
-      (setq headers
-            (sort headers
-                  (lambda (x y)
-                    (< (mail-header-number x) (mail-header-number y)))))
-      (erase-buffer)
-      (mapc 'nnheader-insert-nov headers)
-      'nov)))
-(defvar gnus-article-decode-hook)
-(deffoo nnir-request-article (article &optional group server to-buffer)
-  (nnir-possibly-change-group group server)
-  (if (and (stringp article)
-           (not (eq 'nnimap (car (gnus-server-to-method server)))))
-      (nnheader-report
-       'nnir
-       "nnir-request-article only groks message ids for nnimap servers: %s"
-       server)
-    (save-excursion
-      (let ((article article)
-            query)
-        (when (stringp article)
-          (setq gnus-override-method (gnus-server-to-method server))
-          (setq query
-                (list
-                 (cons 'query (format "HEADER Message-ID %s" article))
-                 (cons 'criteria "")
-                 (cons 'shortcut t)))
-          (unless (and nnir-artlist (equal query nnir-memo-query)
-                       (equal server nnir-memo-server))
-            (setq nnir-artlist (nnir-run-imap query server)
-                  nnir-memo-query query
-                  nnir-memo-server server))
-          (setq article 1))
-        (unless (zerop (nnir-artlist-length nnir-artlist))
-          (let ((artfullgroup (nnir-article-group article))
-                (artno (nnir-article-number article)))
-            (message "Requesting article %d from group %s"
-                     artno artfullgroup)
-            (if to-buffer
-                (with-current-buffer to-buffer
-                  (let ((gnus-article-decode-hook nil))
-                    (gnus-request-article-this-buffer artno artfullgroup)))
-              (gnus-request-article artno artfullgroup))
-            (cons artfullgroup artno)))))))
-(deffoo nnir-request-move-article (article group server accept-form
-                                           &optional last _internal-move-group)
-  (nnir-possibly-change-group group server)
-  (let* ((artfullgroup (nnir-article-group article))
-         (artno (nnir-article-number article))
-         (to-newsgroup (nth 1 accept-form))
-         (to-method (gnus-find-method-for-group to-newsgroup))
-         (from-method (gnus-find-method-for-group artfullgroup))
-         (move-is-internal (gnus-server-equal from-method to-method)))
-    (unless (gnus-check-backend-function
-             'request-move-article artfullgroup)
-      (error "The group %s does not support article moving" artfullgroup))
-    (gnus-request-move-article
-     artno
-     artfullgroup
-     (nth 1 from-method)
-     accept-form
-     last
-     (and move-is-internal
-          to-newsgroup          ; Not respooling
-          (gnus-group-real-name to-newsgroup)))))
-(deffoo nnir-request-expire-articles (articles group &optional server force)
-  (nnir-possibly-change-group group server)
-  (if force
-    (let ((articles-by-group (nnir-categorize
-                              articles nnir-article-group nnir-article-ids))
-          not-deleted)
-      (while (not (null articles-by-group))
-        (let* ((group-articles (pop articles-by-group))
-               (artgroup (car group-articles))
-               (articleids (cadr group-articles))
-               (artlist (sort (mapcar 'cdr articleids) '<)))
-          (unless (gnus-check-backend-function 'request-expire-articles
-                                               artgroup)
-            (error "The group %s does not support article deletion" artgroup))
-          (unless (gnus-check-server (gnus-find-method-for-group artgroup))
-            (error "Couldn't open server for group %s" artgroup))
-          (push (gnus-request-expire-articles
-                 artlist artgroup force)
-                not-deleted)))
-      (sort (delq nil not-deleted) '<))
-    articles))
-(deffoo nnir-warp-to-article ()
-  (nnir-possibly-change-group gnus-newsgroup-name)
-  (let* ((cur (if (> (gnus-summary-article-number) 0)
-                  (gnus-summary-article-number)
-                (error "Can't warp to a pseudo-article")))
-         (backend-article-group (nnir-article-group cur))
-         (backend-article-number (nnir-article-number cur))
-;        (quit-config (gnus-ephemeral-group-p gnus-newsgroup-name))
-         )
-    ;; what should we do here? we could leave all the buffers around
-    ;; and assume that we have to exit from them one by one. or we can
-    ;; try to clean up directly
-    ;;first exit from the nnir summary buffer.
-;    (gnus-summary-exit)
-    ;; and if the nnir summary buffer in turn came from another
-    ;; summary buffer we have to clean that summary up too.
- ;   (when (not (eq (cdr quit-config) 'group))
-;      (gnus-summary-exit))
-    (gnus-summary-read-group-1 backend-article-group t t  nil
-                               nil (list backend-article-number))))
-(deffoo nnir-request-update-mark (_group article mark)
-  (let ((artgroup (nnir-article-group article))
-        (artnumber (nnir-article-number article)))
-    (or (and artgroup
-             artnumber
-             (gnus-request-update-mark artgroup artnumber mark))
-        mark)))
-(deffoo nnir-request-set-mark (group actions &optional server)
-  (nnir-possibly-change-group group server)
-  (let (mlist)
-    (dolist (action actions)
-      (cl-destructuring-bind (range action marks) action
-        (let ((articles-by-group (nnir-categorize
-                                  (gnus-uncompress-range range)
-                                  nnir-article-group nnir-article-number)))
-          (dolist (artgroup articles-by-group)
-            (push (list
-                   (car artgroup)
-                   (list (gnus-compress-sequence
-                          (sort (cadr artgroup) '<))
-                         action marks))
-                  mlist)))))
-    (dolist (request (nnir-categorize  mlist car cadr))
-      (gnus-request-set-mark (car request) (cadr request)))))
-(deffoo nnir-request-update-info (group info &optional server)
-  (nnir-possibly-change-group group server)
-  ;; clear out all existing marks.
-  (setf (gnus-info-marks info) nil)
-  (setf (gnus-info-read info) nil)
-  (let ((group (gnus-group-guess-full-name-from-command-method group))
-        (articles-by-group
-         (nnir-categorize
-          (gnus-uncompress-range (cons 1 (nnir-artlist-length nnir-artlist)))
-          nnir-article-group nnir-article-ids)))
-    (gnus-set-active group
-                     (cons 1 (nnir-artlist-length nnir-artlist)))
-    (while (not (null articles-by-group))
-      (let* ((group-articles (pop articles-by-group))
-             (articleids (reverse (cadr group-articles)))
-             (group-info (gnus-get-info (car group-articles)))
-             (marks (gnus-info-marks group-info))
-             (read (gnus-info-read group-info)))
-        (setf (gnus-info-read info)
-              (gnus-add-to-range
-               (gnus-info-read info)
-               (delq nil
-                     (mapcar
-                      #'(lambda (art)
-                          (when (gnus-member-of-range (cdr art) read)
-                            (car art)))
-                      articleids))))
-        (dolist (mark marks)
-          (cl-destructuring-bind (type . range) mark
-            (gnus-add-marked-articles
-             group type
-             (delq nil
-                     (mapcar
-                      #'(lambda (art)
-                        (when (gnus-member-of-range (cdr art) range) (car art)))
-                      articleids)))))))))
-(deffoo nnir-close-group (group &optional server)
-  (nnir-possibly-change-group group server)
-  (let ((pgroup (gnus-group-guess-full-name-from-command-method group)))
-    (when (and nnir-artlist (not (gnus-ephemeral-group-p pgroup)))
-      (gnus-group-set-parameter  pgroup 'nnir-artlist nnir-artlist))
-    (setq nnir-artlist nil)
-    (when (gnus-ephemeral-group-p pgroup)
-      (gnus-kill-ephemeral-group pgroup)
-      (setq gnus-ephemeral-servers
-            (delq (assq 'nnir gnus-ephemeral-servers)
-                  gnus-ephemeral-servers)))))
-;; (gnus-opened-servers-remove
-;;  (car (assoc  '(nnir "nnir-ephemeral" (nnir-address "nnir"))
-;;              gnus-opened-servers))))
 (defmacro nnir-add-result (dirnam artno score prefix server artlist)
-  "Ask `nnir-compose-result' to construct a result vector,
+  "Construct a result vector and add it to ARTLIST.
-and if it is non-nil, add it to ARTLIST."
+DIRNAM, ARTNO, SCORE, PREFIX and SERVER are passed to
+`nnir-compose-result' to make the vector.  Only add the result if
+non-nil."
  `(let ((result (nnir-compose-result ,dirnam ,artno ,score ,prefix ,server)))
     (when (not (null result))
       (push result ,artlist))))
@@ -940,9 +498,9 @@ and if it is non-nil, add it to ARTLIST."
 ;; Helper function currently used by the Swish++ and Namazu backends;
 ;; perhaps useful for other backends as well
 (defun nnir-compose-result (dirnam article score prefix server)
-  "Extract the group from DIRNAM, and create a result vector
+  "Construct a result vector.
-ready to be added to the list of search results."
+The DIRNAM, ARTICLE, SCORE, PREFIX, and SERVER are used to
+construct the vector entries."
  ;; remove nnir-*-remove-prefix from beginning of dirnam filename
  (when (string-match (concat "^" prefix) dirnam)
    (setq dirnam (replace-match "" t t dirnam)))
@@ -977,13 +535,14 @@ ready to be added to the list of search results."
 ;; imap interface
 (defun nnir-run-imap (query srv &optional groups)
-  "Run a search against an IMAP back-end server.
+  "Run the QUERY search against an IMAP back-end server SRV.
-This uses a custom query language parser; see `nnir-imap-make-query'
+Search GROUPS, or all active groups on SRV if GROUPS is nil.
-for details on the language and supported extensions."
+This uses a custom query language parser; see
+`nnir-imap-make-query' for details on the language and supported
+extensions."
  (save-excursion
    (let ((qstring (cdr (assq 'query query)))
          (server (cadr (gnus-server-to-method srv)))
-;;          (defs (nth 2 (gnus-server-to-method srv)))
          (criteria (or (cdr (assq 'criteria query))
                        (cdr (assoc nnir-imap-default-search-key
                                    nnir-imap-search-arguments))))
@@ -995,38 +554,37 @@ for details on the language and supported extensions."
       (catch 'found
         (mapcar
          #'(lambda (group)
-            (let (artlist)
+              (let (artlist)
-              (condition-case ()
+                (condition-case ()
-                  (when (nnimap-change-group
+                    (when (nnimap-change-group
-                         (gnus-group-short-name group) server)
+                           (gnus-group-short-name group) server)
-                    (with-current-buffer (nnimap-buffer)
+                      (with-current-buffer (nnimap-buffer)
-                      (message "Searching %s..." group)
+                        (message "Searching %s..." group)
-                      (let ((arts 0)
+                        (let ((arts 0)
-                            (result (nnimap-command "UID SEARCH %s"
+                              (result (nnimap-command "UID SEARCH %s"
-                                                    (if (string= criteria "")
+                                                      (if (string= criteria "")
-                                                        qstring
+                                                          qstring
-                                                      (nnir-imap-make-query
+                                                        (nnir-imap-make-query
-                                                       criteria qstring)))))
+                                                         criteria qstring)))))
-                        (mapc
+                          (mapc
-                         (lambda (artnum)
+                           (lambda (artnum)
-                           (let ((artn (string-to-number artnum)))
+                             (let ((artn (string-to-number artnum)))
-                             (when (> artn 0)
+                               (when (> artn 0)
-                               (push (vector group artn 100)
+                                 (push (vector group artn 100)
-                                     artlist)
+                                       artlist)
-                               (when (assq 'shortcut query)
+                                 (when (assq 'shortcut query)
-                                 (throw 'found (list artlist)))
+                                   (throw 'found (list artlist)))
-                               (setq arts (1+ arts)))))
+                                 (setq arts (1+ arts)))))
-                         (and (car result)
+                           (and (car result)
-                              (cdr (assoc "SEARCH" (cdr result)))))
+                                (cdr (assoc "SEARCH" (cdr result)))))
-                        (message "Searching %s... %d matches" group arts)))
+                          (message "Searching %s... %d matches" group arts)))
-                    (message "Searching %s...done" group))
+                      (message "Searching %s...done" group))
-                (quit nil))
+                  (quit nil))
-              (nreverse artlist)))
+                (nreverse artlist)))
          groups))))))
 (defun nnir-imap-make-query (criteria qstring)
-  "Parse the query string and criteria into an appropriate IMAP search
+  "Make an IMAP search expression from QSTRING and CRITERIA.
-expression, returning the string query to make.
 This implements a little language designed to return the expected
 results to an arbitrary query string to the end user.
@@ -1063,7 +621,7 @@ In the future the following will be added to the language:
 (defun nnir-imap-query-to-imap (criteria query)
-  "Turn an s-expression format QUERY into IMAP."
+  "Turn an s-expression format QUERY with CRITERIA into IMAP."
  (mapconcat
   ;; Turn the expressions into IMAP text
   (lambda (item)
@@ -1099,8 +657,9 @@ In the future the following will be added to the language:
 (defun nnir-imap-parse-query (string)
-  "Turn STRING into an s-expression based query based on the IMAP
+  "Turn STRING into an s-expression query.
-query language as defined in `nnir-imap-make-query'.
+STRING is based on the IMAP query language as defined in
+`nnir-imap-make-query'.
 This involves turning individual tokens into higher level terms
 that the search language can then understand and use."
@@ -1116,7 +675,7 @@ that the search language can then understand and use."
 (defun nnir-imap-next-expr (&optional count)
-  "Return the next expression from the current buffer."
+  "Return the next (COUNT) expression from the current buffer."
  (let ((term (nnir-imap-next-term count))
        (next (nnir-imap-peek-symbol)))
    ;; Are we looking at an 'or' expression?
@@ -1129,7 +688,7 @@ that the search language can then understand and use."
 (defun nnir-imap-next-term (&optional count)
-  "Return the next term from the current buffer."
+  "Return the next (COUNT) term from the current buffer."
  (let ((term (nnir-imap-next-symbol count)))
    ;; What sort of term is this?
    (cond
@@ -1147,9 +706,10 @@ that the search language can then understand and use."
    (nnir-imap-next-symbol)))
 (defun nnir-imap-next-symbol (&optional count)
-  "Return the next symbol from the current buffer, or nil if we are
+  "Return the next (COUNT) symbol from the current buffer.
-at the end of the buffer.  If supplied COUNT skips some symbols before
+Return nil if we are at the end of the buffer.  If supplied COUNT
-returning the one at the supplied position."
+skips some symbols before returning the one at the supplied
+position."
  (when (and (numberp count) (> count 1))
    (nnir-imap-next-symbol (1- count)))
  (let ((case-fold-search t))
@@ -1180,7 +740,7 @@ returning the one at the supplied position."
            (buffer-substring start end)))))))
 (defun nnir-imap-delimited-string (delimiter)
-  "Return a delimited string from the current buffer."
+  "Return a string delimited by DELIMITER from the current buffer."
  (let ((start (point)) end)
    (forward-char 1)                    ; skip the first delimiter.
    (while (not end)
@@ -1207,7 +767,7 @@ returning the one at the supplied position."
 ;; - file size
 ;; - group
 (defun nnir-run-swish++ (query server &optional _group)
-  "Run QUERY against swish++.
+  "Run QUERY on SERVER against swish++.
 Returns a vector of (group name, file name) pairs (also vectors,
 actually).
@@ -1297,7 +857,7 @@ Windows NT 4.0."
 ;; Swish-E interface.
 (defun nnir-run-swish-e (query server &optional _group)
-  "Run given QUERY against swish-e.
+  "Run given QUERY on SERVER against swish-e.
 Returns a vector of (group name, file name) pairs (also vectors,
 actually).
@@ -1392,6 +952,7 @@ Tested with swish-e-2.0.1 on Windows NT 4.0."
 ;; HyREX interface
 (defun nnir-run-hyrex (query server &optional group)
+  "Run given QUERY with GROUP on SERVER against hyrex."
  (save-excursion
    (let ((artlist nil)
          (groupspec (cdr (assq 'hyrex-group query)))
@@ -1463,7 +1024,7 @@ Tested with swish-e-2.0.1 on Windows NT 4.0."
 ;; Namazu interface
 (defun nnir-run-namazu (query server &optional _group)
-  "Run given QUERY against Namazu.
+  "Run QUERY on SERVER  against Namazu.
 Returns a vector of (group name, file name) pairs (also vectors,
 actually).
@@ -1533,7 +1094,7 @@ Tested with Namazu 2.0.6 on a GNU/Linux system."
                                  (nnir-artitem-rsv y)))))))))
 (defun nnir-run-notmuch (query server &optional groups)
-  "Run QUERY against notmuch.
+  "Run QUERY with  GROUPS from SERVER  against notmuch.
 Returns a vector of (group name, file name) pairs (also vectors,
 actually).  If GROUPS is a list of group names, use them to
 construct path: search terms (see the variable
@@ -1617,7 +1178,7 @@ construct path: search terms (see the variable
      artlist)))
 (defun nnir-run-find-grep (query server &optional grouplist)
-  "Run find and grep to obtain matching articles."
+  "Run find and grep to QUERY GROUPLIST on SERVER for matching articles."
  (let* ((method (gnus-server-to-method server))
         (sym (intern
               (concat (symbol-name (car method)) "-directory")))
@@ -1703,14 +1264,10 @@ construct path: search terms (see the variable
 ;;; Util Code:
-(defun gnus-nnir-group-p (group)
-  "Say whether GROUP is nnir or not."
-  (if (gnus-group-prefixed-p group)
-      (eq 'nnir (car (gnus-find-method-for-group group)))
-    (and group (string-match "^nnir" group))))
 (defun nnir-read-parms (nnir-search-engine)
-  "Read additional search parameters according to `nnir-engines'."
+  "Read additional search parameters for NNIR-SEARCH-ENGINE.
+Parameters are according to `nnir-engines'."
  (let ((parmspec (nth 2 (assoc nnir-search-engine nnir-engines))))
    (mapcar #'nnir-read-parm parmspec)))
@@ -1727,7 +1284,7 @@ PARMSPEC is a cons cell, the car is a symbol, the cdr is a prompt."
      (cons sym (read-string prompt)))))
 (defun nnir-run-query (specs)
-  "Invoke appropriate search engine function (see `nnir-engines')."
+  "Invoke search engine appropriate for SPECS (see `nnir-engines')."
  (apply #'vconcat
         (mapcar
          (lambda (x)
@@ -1736,10 +1293,11 @@ PARMSPEC is a cons cell, the car is a symbol, the cdr is a prompt."
                   (search-func (cadr (assoc search-engine nnir-engines))))
              (and search-func
                   (funcall search-func (cdr (assq 'nnir-query-spec specs))
-                            server (cadr x)))))
+                            server (cdr x)))))
          (cdr (assq 'nnir-group-spec specs)))))
 (defun nnir-server-to-search-engine (server)
+  "Find search engine for SERVER."
  (or (nnir-read-server-parm 'nnir-search-engine server t)
      (cdr (assoc (car (gnus-server-to-method server))
                  nnir-method-default-engines))))
@@ -1754,48 +1312,10 @@ environment unless NOT-GLOBAL is non-nil."
          ((and (not not-global) (boundp key)) (symbol-value key))
          (t nil))))
-(defun nnir-possibly-change-group (group &optional server)
+(autoload 'gnus-request-list "gnus-int")
-  (or (not server) (nnir-server-opened server) (nnir-open-server server))
-  (when (gnus-nnir-group-p group)
-    (setq nnir-artlist (gnus-group-get-parameter
-                        (gnus-group-prefixed-name
-                         (gnus-group-short-name group) '(nnir "nnir"))
-                        'nnir-artlist t))))
-(defun nnir-server-opened (&optional server)
-  (let ((backend (car (gnus-server-to-method server))))
-    (nnoo-current-server-p (or backend 'nnir) server)))
-(autoload 'nnimap-make-thread-query "nnimap")
-(declare-function gnus-registry-get-id-key "gnus-registry" (id key))
-(defun nnir-search-thread (header)
-  "Make an nnir group based on the thread containing the article HEADER.
-The current server will be searched.  If the registry is installed,
-the server that the registry reports the current article came from
-is also searched."
-  (let* ((query
-          (list (cons 'query (nnimap-make-thread-query header))
-                (cons 'criteria "")))
-         (server
-          (list (list (gnus-method-to-server
-           (gnus-find-method-for-group gnus-newsgroup-name)))))
-         (registry-group (and
-                          (bound-and-true-p gnus-registry-enabled)
-                          (car (gnus-registry-get-id-key
-                                (mail-header-id header) 'group))))
-         (registry-server
-          (and registry-group
-               (gnus-method-to-server
-                (gnus-find-method-for-group registry-group)))))
-    (when registry-server
-      (cl-pushnew (list registry-server) server :test #'equal))
-    (gnus-group-make-nnir-group nil (list
-                                     (cons 'nnir-query-spec query)
-                                     (cons 'nnir-group-spec server)))
-    (gnus-summary-goto-subject (gnus-id-to-article (mail-header-id header)))))
 (defun nnir-get-active (srv)
+  "Return the active list for SRV."
  (let ((method (gnus-server-to-method srv))
        groups)
    (gnus-request-list method)
@@ -1835,82 +1355,37 @@ is also searched."
            (forward-line)))))
    groups))
-;; Behind gnus-registry-enabled test.
+(autoload 'nnselect-categorize "nnselect" nil nil)
-(declare-function gnus-registry-action "gnus-registry"
+(autoload 'gnus-group-topic-name "gnus-topic" nil nil)
-                  (action data-header from &optional to method))
+(defvar gnus-group-marked)
+(defvar gnus-topic-alist)
-(defun nnir-registry-action (action data-header _from &optional to method)
-  "Call `gnus-registry-action' with the original article group."
+(defun nnir-make-specs (nnir-extra-parms &optional specs)
-  (gnus-registry-action
+  "Make the query-spec and group-spec for a search with NNIR-EXTRA-PARMS.
-   action
+Query for the specs, or use SPECS."
-   data-header
+  (let* ((group-spec
-   (nnir-article-group (mail-header-number data-header))
+          (or (cdr (assq 'nnir-group-spec specs))
-   to
+              (if (gnus-server-server-name)
-   method))
+                  (list (list (gnus-server-server-name)))
+                (nnselect-categorize
-(defun nnir-mode ()
+                 (or gnus-group-marked
-  (when (eq (car (gnus-find-method-for-group gnus-newsgroup-name)) 'nnir)
+                     (if (gnus-group-group-name)
-    (when (and nnir-summary-line-format
+                         (list (gnus-group-group-name))
-               (not (string= nnir-summary-line-format
+                       (cdr (assoc (gnus-group-topic-name) gnus-topic-alist))))
-                             gnus-summary-line-format)))
+                 'nnselect-group-server))))
-      (setq gnus-summary-line-format nnir-summary-line-format)
+         (query-spec
-      (gnus-update-format-specifications nil 'summary))
+          (or (cdr (assq 'nnir-query-spec specs))
-    (when (bound-and-true-p gnus-registry-enabled)
+              (apply
-      (remove-hook 'gnus-summary-article-delete-hook 'gnus-registry-action t)
+               'append
-      (remove-hook 'gnus-summary-article-move-hook 'gnus-registry-action t)
+               (list (cons 'query
-      (remove-hook 'gnus-summary-article-expire-hook 'gnus-registry-action t)
+                           (read-string "Query: " nil 'nnir-search-history)))
-      (add-hook 'gnus-summary-article-delete-hook 'nnir-registry-action t t)
+               (when nnir-extra-parms
-      (add-hook 'gnus-summary-article-move-hook 'nnir-registry-action t t)
+                 (mapcar
-      (add-hook 'gnus-summary-article-expire-hook 'nnir-registry-action t t))))
+                  (lambda (x)
+                    (nnir-read-parms (nnir-server-to-search-engine (car x))))
+                  group-spec))))))
-(defun gnus-summary-create-nnir-group ()
+    (list (cons 'nnir-query-spec query-spec)
-  (interactive)
+          (cons 'nnir-group-spec group-spec))))
-  (or (nnir-server-opened "") (nnir-open-server "nnir"))
-  (let ((name (gnus-read-group "Group name: "))
-        (method '(nnir ""))
-        (pgroup
-         (gnus-group-guess-full-name-from-command-method gnus-newsgroup-name)))
-    (with-current-buffer gnus-group-buffer
-      (gnus-group-make-group
-       name method nil
-       (gnus-group-find-parameter pgroup)))))
-(deffoo nnir-request-create-group (group &optional _server args)
-  (message "Creating nnir group %s" group)
-  (let* ((group (gnus-group-prefixed-name  group '(nnir "nnir")))
-         (specs (assq 'nnir-specs args))
-         (query-spec
-          (or (cdr (assq 'nnir-query-spec specs))
-              (list (cons 'query
-                          (read-string "Query: " nil 'nnir-search-history)))))
-         (group-spec
-          (or (cdr (assq 'nnir-group-spec specs))
-              (list (list (read-string "Server: " nil nil)))))
-         (nnir-specs (list (cons 'nnir-query-spec query-spec)
-                           (cons 'nnir-group-spec group-spec))))
-    (gnus-group-set-parameter group 'nnir-specs nnir-specs)
-    (gnus-group-set-parameter
-     group 'nnir-artlist
-     (or (cdr (assq 'nnir-artlist args))
-         (nnir-run-query nnir-specs)))
-    (nnir-request-update-info group (gnus-get-info group)))
-  t)
-(deffoo nnir-request-delete-group (_group &optional _force _server)
-  t)
-(deffoo nnir-request-list (&optional _server)
-  t)
-(deffoo nnir-request-scan (_group _method)
-  t)
-(deffoo nnir-request-close ()
-  t)
-(nnoo-define-skeleton nnir)
 ;; The end.
 (provide 'nnir)
diff --git a/lisp/gnus/nnmaildir.el b/lisp/gnus/nnmaildir.el
index 9c7b1254413..81a148db669 100644
--- a/lisp/gnus/nnmaildir.el
+++ b/lisp/gnus/nnmaildir.el
@@ -492,7 +492,7 @@ This variable is set by `nnmaildir-request-article'.")
            (setq nov-mid 0))
          (goto-char (point-min))
          (delete-char 1)
-          (setq nov (nnheader-parse-naked-head)
+          (setq nov (nnheader-parse-head t)
                field (or (mail-header-lines nov) 0)))
        (unless (or (zerop field) (nnmaildir--param pgname 'distrust-Lines:))
          (setq nov-mid field))
diff --git a/lisp/gnus/nnml.el b/lisp/gnus/nnml.el
index baf5d54b74d..ad608b6575e 100644
--- a/lisp/gnus/nnml.el
+++ b/lisp/gnus/nnml.el
@@ -766,7 +766,7 @@ article number.  This function is called narrowed to an article."
         (if (re-search-forward "\n\r?\n" nil t)
             (1- (point))
           (point-max))))
-      (let ((headers (nnheader-parse-naked-head)))
+      (let ((headers (nnheader-parse-head t)))
        (setf (mail-header-chars  headers) chars)
        (setf (mail-header-number headers) number)
        headers))))
diff --git a/lisp/gnus/nnselect.el b/lisp/gnus/nnselect.el
new file mode 100644
index 00000000000..460bc63132c
--- /dev/null
+++ b/lisp/gnus/nnselect.el
@@ -0,0 +1,864 @@
+;;; nnselect.el --- a virtual group backend   -*- lexical-binding:t -*-
+;; Copyright (C) 2020 Free Software Foundation, Inc.
+;; Author: Andrew Cohen <cohen@andy.bu.edu>
+;; Keywords: news mail
+;; This file is part of GNU Emacs.
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+;;; Commentary:
+;; This is a "virtual" backend that allows an aribtrary list of
+;; articles to be treated as a gnus group.  An nnselect group uses an
+;; nnselect-spec group parameter to specify this list of
+;; articles.  nnselect-spec is an alist with two keys:
+;; nnselect-function, whose value should be a function that returns
+;; the list of articles, and nnselect-args.  The function will be
+;; applied to the arguments to generate the list of articles.  The
+;; return value should be a vector, each element of which should in
+;; turn be a vector of three elements: a real prefixed group name, an
+;; article number in that group, and an integer score.  The score is
+;; not used by nnselect but may be used by other code to help in
+;; sorting.  Most functions will just chose a fixed number, such as
+;; 100, for this score.
+;; For example the search function `nnir-run-query' applied to
+;; arguments specifying a search query (see "nnir.el") can be used to
+;; return a list of articles from a search.  Or the function can be the
+;; identity and the args a vector of articles.
+;;; Code:
+;;; Setup:
+(require 'gnus-art)
+(require 'nnir)
+(eval-when-compile (require 'cl-lib))
+;; Set up the backend
+(nnoo-declare nnselect)
+(nnoo-define-basics nnselect)
+(gnus-declare-backend "nnselect" 'post-mail 'virtual)
+;;; Internal Variables:
+(defvar gnus-inhibit-demon)
+(defvar gnus-message-group-art)
+;; For future use
+(defvoo nnselect-directory gnus-directory
+  "Directory for the nnselect backend.")
+(defvoo nnselect-active-file
+    (expand-file-name "nnselect-active" nnselect-directory)
+  "nnselect active file.")
+(defvoo nnselect-groups-file
+    (expand-file-name "nnselect-newsgroups" nnselect-directory)
+  "nnselect groups description file.")
+;;; Helper routines.
+(defun nnselect-compress-artlist (artlist)
+  "Compress ARTLIST."
+  (let (selection)
+    (pcase-dolist (`(,artgroup . ,arts)
+                   (nnselect-categorize artlist 'nnselect-artitem-group))
+      (let (list)
+        (pcase-dolist (`(,rsv . ,articles)
+                       (nnselect-categorize
+                        arts 'nnselect-artitem-rsv 'nnselect-artitem-number))
+          (push (cons rsv (gnus-compress-sequence (sort articles '<)))
+                list))
+        (push (cons artgroup list) selection)))
+    selection))
+(defun nnselect-uncompress-artlist (artlist)
+  "Uncompress ARTLIST."
+  (if (vectorp artlist)
+      artlist
+    (let (selection)
+      (pcase-dolist (`(,artgroup (,artrsv . ,artseq)) artlist)
+        (setq selection
+              (vconcat
+               (cl-map 'vector
+                    #'(lambda (art)
+                        (vector artgroup art artrsv))
+                    (gnus-uncompress-sequence artseq)) selection)))
+      selection)))
+(defun nnselect-group-server (group)
+  "Return the server for GROUP."
+  (gnus-group-server group))
+;; Data type article list.
+(define-inline nnselect-artlist-length (artlist)
+    (inline-quote (length ,artlist)))
+(define-inline nnselect-artlist-article (artlist n)
+  "Return from ARTLIST the Nth artitem (counting starting at 1)."
+  (inline-quote (when (> ,n 0)
+                  (elt ,artlist (1- ,n)))))
+(define-inline nnselect-artitem-group (artitem)
+  "Return the group from the ARTITEM."
+  (inline-quote (elt ,artitem 0)))
+(define-inline nnselect-artitem-number (artitem)
+  "Return the number from the ARTITEM."
+  (inline-quote (elt ,artitem 1)))
+(define-inline nnselect-artitem-rsv (artitem)
+  "Return the Retrieval Status Value (RSV, score) from the ARTITEM."
+  (inline-quote (elt ,artitem 2)))
+(define-inline nnselect-article-group (article)
+  "Return the group for ARTICLE."
+  (inline-quote
+   (nnselect-artitem-group  (nnselect-artlist-article
+                             gnus-newsgroup-selection ,article))))
+(define-inline nnselect-article-number (article)
+  "Return the number for ARTICLE."
+  (inline-quote (nnselect-artitem-number
+                 (nnselect-artlist-article
+                  gnus-newsgroup-selection ,article))))
+(define-inline nnselect-article-rsv (article)
+  "Return the rsv for ARTICLE."
+  (inline-quote (nnselect-artitem-rsv
+                 (nnselect-artlist-article
+                  gnus-newsgroup-selection ,article))))
+(define-inline nnselect-article-id (article)
+  "Return the pair `(nnselect id . real id)' of ARTICLE."
+  (inline-quote (cons ,article (nnselect-article-number ,article))))
+(define-inline nnselect-categorize (sequence keyfunc &optional valuefunc)
+  "Sorts a sequence into categories.
+Returns a list of the form
+`((key1 (element11 element12)) (key2 (element21 element22))'.
+The category key for a member of the sequence is obtained
+as `(keyfunc member)' and the corresponding element is just
+`member' (or `(valuefunc member)' if `valuefunc' is non-nil)."
+  (inline-letevals (sequence keyfunc valuefunc)
+    (inline-quote  (let ((valuefunc (or ,valuefunc 'identity))
+                         result)
+                     (unless (null ,sequence)
+                      (mapc
+                       (lambda (member)
+                         (let* ((key (funcall ,keyfunc member))
+                                (value  (funcall valuefunc member))
+                                (kr (assoc key result)))
+                           (if kr
+                               (push value (cdr kr))
+                             (push (list key value) result))))
+                       (reverse ,sequence))
+                      result)))))
+;; Unclear whether a macro or an inline function is best.
+;; (defmacro nnselect-categorize (sequence keyfunc &optional valuefunc)
+;;   "Sorts a sequence into categories and returns a list of the form
+;; `((key1 (element11 element12)) (key2 (element21 element22))'.
+;; The category key for a member of the sequence is obtained
+;; as `(keyfunc member)' and the corresponding element is just
+;; `member' (or `(valuefunc member)' if `valuefunc' is non-nil)."
+;;   (let ((key (make-symbol "key"))
+;;      (value (make-symbol "value"))
+;;      (result (make-symbol "result"))
+;;      (valuefunc (or valuefunc 'identity)))
+;;     `(unless (null ,sequence)
+;;        (let (,result)
+;;       (mapc
+;;        (lambda (member)
+;;          (let* ((,key (,keyfunc member))
+;;                 (,value  (,valuefunc member))
+;;                 (kr (assoc ,key ,result)))
+;;            (if kr
+;;                (push ,value (cdr kr))
+;;              (push (list ,key ,value) ,result))))
+;;        (reverse ,sequence))
+;;       ,result))))
+(define-inline ids-by-group (articles)
+  (inline-quote
+   (nnselect-categorize ,articles 'nnselect-article-group
+                        'nnselect-article-id)))
+(define-inline numbers-by-group (articles)
+  (inline-quote
+   (nnselect-categorize
+    ,articles 'nnselect-article-group 'nnselect-article-number)))
+(defmacro nnselect-add-prefix (group)
+  "Ensures that the GROUP has an nnselect prefix."
+  `(gnus-group-prefixed-name
+   (gnus-group-short-name ,group) '(nnselect "nnselect")))
+(defmacro nnselect-get-artlist (group)
+  "Retrieve the list of articles for GROUP."
+  `(when (gnus-nnselect-group-p ,group)
+     (nnselect-uncompress-artlist
+      (gnus-group-get-parameter ,group 'nnselect-artlist t))))
+(defmacro nnselect-add-novitem (novitem)
+  "Add NOVITEM to the list of headers."
+  `(let* ((novitem ,novitem)
+          (artno (and novitem
+                      (mail-header-number novitem)))
+          (art (car-safe (rassq artno artids))))
+     (when art
+       (setf (mail-header-number novitem) art)
+       (push novitem headers))))
+;;; User Customizable Variables:
+(defgroup nnselect nil
+  "Virtual groups in Gnus with arbitrary selection methods."
+  :group 'gnus)
+(defcustom nnselect-retrieve-headers-override-function nil
+  "A function that retrieves article headers for ARTICLES from GROUP.
+The retrieved headers should populate the `nntp-server-buffer'.
+Returns either the retrieved header format 'nov or 'headers.
+If this variable is nil, or if the provided function returns nil,
+  `gnus-retrieve-headers' will be called instead."
+  :version "24.1" :type '(function) :group 'nnselect)
+;; Gnus backend interface functions.
+(deffoo nnselect-open-server (server &optional definitions)
+  ;; Just set the server variables appropriately.
+  (let ((backend (or (car (gnus-server-to-method server)) 'nnselect)))
+    (nnoo-change-server backend server definitions)))
+;; (deffoo nnselect-server-opened (&optional server)
+;;   "Is SERVER the current virtual server?"
+;;   (if (string-empty-p server)
+;;       t
+;;     (let ((backend (car (gnus-server-to-method server))))
+;;      (nnoo-current-server-p (or backend 'nnselect) server))))
+(deffoo nnselect-server-opened (&optional _server)
+  t)
+(deffoo nnselect-request-group (group &optional _server _dont-check info)
+  (let* ((group (nnselect-add-prefix group))
+         (nnselect-artlist (nnselect-get-artlist group))
+         length)
+    ;; Check for cached select result or run the selection and cache
+    ;; the result.
+    (unless nnselect-artlist
+      (gnus-group-set-parameter
+       group 'nnselect-artlist
+       (nnselect-compress-artlist (setq nnselect-artlist
+             (nnselect-run
+              (gnus-group-get-parameter group 'nnselect-specs t)))))
+      (nnselect-request-update-info
+       group (or info (gnus-get-info group))))
+    (if (zerop (setq length (nnselect-artlist-length nnselect-artlist)))
+        (progn
+          (nnheader-report 'nnselect "Selection produced empty results.")
+          (nnheader-insert ""))
+      (with-current-buffer nntp-server-buffer
+        (nnheader-insert "211 %d %d %d %s\n"
+                         length    ; total #
+                         1         ; first #
+                         length    ; last #
+                         group))) ; group name
+  nnselect-artlist))
+(deffoo nnselect-retrieve-headers (articles group &optional _server fetch-old)
+  (let ((group (nnselect-add-prefix group)))
+    (with-current-buffer (gnus-summary-buffer-name group)
+      (setq gnus-newsgroup-selection (or gnus-newsgroup-selection
+                                         (nnselect-get-artlist group)))
+      (let ((gnus-inhibit-demon t)
+            (gartids (ids-by-group articles))
+            headers)
+        (with-current-buffer nntp-server-buffer
+          (pcase-dolist (`(,artgroup . ,artids) gartids)
+            (let ((artlist (sort (mapcar 'cdr artids) '<))
+                  (gnus-override-method (gnus-find-method-for-group artgroup))
+                  (fetch-old
+                   (or
+                    (car-safe
+                     (gnus-group-find-parameter artgroup
+                                                'gnus-fetch-old-headers t))
+                    fetch-old)))
+              (erase-buffer)
+              (pcase (setq gnus-headers-retrieved-by
+                           (or
+                            (and
+                             nnselect-retrieve-headers-override-function
+                             (funcall
+                              nnselect-retrieve-headers-override-function
+                              artlist artgroup))
+                            (gnus-retrieve-headers
+                             artlist artgroup fetch-old)))
+                ('nov
+                 (goto-char (point-min))
+                 (while (not (eobp))
+                   (nnselect-add-novitem
+                    (nnheader-parse-nov))
+                   (forward-line 1)))
+                ('headers
+                 (goto-char (point-min))
+                 (while (not (eobp))
+                   (nnselect-add-novitem
+                    (nnheader-parse-head))
+                   (forward-line 1)))
+                ((pred listp)
+                 (dolist (novitem gnus-headers-retrieved-by)
+                   (nnselect-add-novitem novitem)))
+                (_ (error "Unknown header type %s while requesting articles \
+                    of group %s" gnus-headers-retrieved-by artgroup)))))
+          (setq headers
+                (sort
+                 headers
+                 (lambda (x y)
+                   (< (mail-header-number x) (mail-header-number y))))))))))
+(deffoo nnselect-request-article (article &optional _group server to-buffer)
+  (let* ((gnus-override-method nil)
+         servers group-art artlist)
+    (if (numberp article)
+        (with-current-buffer gnus-summary-buffer
+          (unless (zerop (nnselect-artlist-length
+                          gnus-newsgroup-selection))
+            (setq group-art (cons (nnselect-article-group article)
+                                  (nnselect-article-number article)))))
+      ;; message-id: either coming from a referral or a pseudo-article
+      ;; find the servers for a pseudo-article
+      (if (eq 'nnselect (car (gnus-server-to-method server)))
+          (with-current-buffer gnus-summary-buffer
+            (let ((thread  (gnus-id-to-thread article)))
+              (when thread
+                (mapc
+                 #'(lambda (x)
+                     (when (and x (> x 0))
+                       (cl-pushnew
+                        (list
+                         (gnus-method-to-server
+                          (gnus-find-method-for-group
+                           (nnselect-article-group x)))) servers :test 'equal)))
+                 (gnus-articles-in-thread thread)))))
+        (setq servers (list (list server))))
+      (setq artlist
+            (nnir-run-query
+             (list
+              (cons 'nnir-query-spec
+                    (list (cons 'query  (format "HEADER Message-ID %s" article))
+                    (cons 'criteria "")  (cons 'shortcut t)))
+              (cons 'nnir-group-spec servers))))
+      (unless (zerop (nnselect-artlist-length artlist))
+        (setq
+         group-art
+         (cons
+          (nnselect-artitem-group (nnselect-artlist-article  artlist 1))
+          (nnselect-artitem-number (nnselect-artlist-article  artlist 1))))))
+    (when (numberp (cdr group-art))
+      (message "Requesting article %d from group %s"
+               (cdr group-art) (car group-art))
+      (if to-buffer
+          (with-current-buffer to-buffer
+            (let ((gnus-article-decode-hook nil))
+              (gnus-request-article-this-buffer
+               (cdr group-art) (car group-art))))
+        (gnus-request-article (cdr group-art) (car group-art)))
+      group-art)))
+(deffoo nnselect-request-move-article
+    (article _group _server accept-form &optional last _internal-move-group)
+  (let* ((artgroup (nnselect-article-group article))
+         (artnumber (nnselect-article-number article))
+         (to-newsgroup (nth 1 accept-form))
+         (to-method (gnus-find-method-for-group to-newsgroup))
+         (from-method (gnus-find-method-for-group artgroup))
+         (move-is-internal (gnus-server-equal from-method to-method)))
+    (unless (gnus-check-backend-function
+             'request-move-article artgroup)
+      (error "The group %s does not support article moving" artgroup))
+    (gnus-request-move-article
+     artnumber
+     artgroup
+     (nth 1 from-method)
+     accept-form
+     last
+     (and move-is-internal
+          to-newsgroup          ; Not respooling
+          (gnus-group-real-name to-newsgroup)))))
+(deffoo nnselect-request-expire-articles
+    (articles _group &optional _server force)
+  (if force
+      (let (not-expired)
+        (pcase-dolist (`(,artgroup . ,artids) (ids-by-group articles))
+          (let ((artlist (sort (mapcar 'cdr artids) '<)))
+            (unless (gnus-check-backend-function 'request-expire-articles
+                                                 artgroup)
+              (error "Group %s does not support article expiration" artgroup))
+            (unless (gnus-check-server (gnus-find-method-for-group artgroup))
+              (error "Couldn't open server for group %s" artgroup))
+            (push (mapcar #'(lambda (art)
+                              (car (rassq art artids)))
+                          (let ((nnimap-expunge 'immediately))
+                            (gnus-request-expire-articles
+                             artlist artgroup force)))
+                  not-expired)))
+        (sort (delq nil not-expired) '<))
+    articles))
+(deffoo nnselect-warp-to-article ()
+  (let* ((cur (if (> (gnus-summary-article-number) 0)
+                  (gnus-summary-article-number)
+                (error "Can't warp to a pseudo-article")))
+         (artgroup (nnselect-article-group cur))
+         (artnumber (nnselect-article-number cur))
+         (_quit-config (gnus-ephemeral-group-p gnus-newsgroup-name)))
+    ;; what should we do here? we could leave all the buffers around
+    ;; and assume that we have to exit from them one by one. or we can
+    ;; try to clean up directly
+    ;;first exit from the nnselect summary buffer.
+    ;;(gnus-summary-exit)
+    ;; and if the nnselect summary buffer in turn came from another
+    ;; summary buffer we have to clean that summary up too.
+    ;;(when (not (eq (cdr quit-config) 'group))
+    ;;  (gnus-summary-exit))
+    (gnus-summary-read-group-1 artgroup t t  nil
+                               nil (list artnumber))))
+;; we pass this through to the real group in case it wants to adjust
+;; the mark. We also use this to mark an article expirable iff it is
+;; expirable in the real group.
+(deffoo nnselect-request-update-mark (_group article mark)
+  (let* ((artgroup (nnselect-article-group article))
+         (artnumber (nnselect-article-number article))
+         (gmark (gnus-request-update-mark artgroup artnumber mark)))
+    (when (and artnumber
+               (memq mark gnus-auto-expirable-marks)
+               (= mark gmark)
+               (gnus-group-auto-expirable-p artgroup))
+      (setq gmark gnus-expirable-mark))
+    gmark))
+(deffoo nnselect-request-set-mark (_group actions &optional _server)
+  (mapc
+   (lambda (request) (gnus-request-set-mark (car request) (cdr request)))
+   (nnselect-categorize
+    (cl-mapcan
+     (lambda (act)
+       (cl-destructuring-bind (range action marks) act
+         (mapcar
+          (lambda (artgroup)
+            (list (car artgroup)
+                  (gnus-compress-sequence (sort (cdr artgroup) '<))
+                  action marks))
+          (numbers-by-group
+           (gnus-uncompress-range range)))))
+     actions)
+    'car 'cdr)))
+(deffoo nnselect-request-update-info (group info &optional _server)
+  (let* ((group  (nnselect-add-prefix group))
+         (gnus-newsgroup-selection (or gnus-newsgroup-selection
+                                       (nnselect-get-artlist group))))
+    (gnus-info-set-marks info nil)
+    (setf (gnus-info-read info) nil)
+    (pcase-dolist (`(,artgroup . ,nartids)
+                   (ids-by-group
+                    (number-sequence 1 (nnselect-artlist-length
+                                        gnus-newsgroup-selection))))
+      (let* ((gnus-newsgroup-active nil)
+             (artids (cl-sort nartids '< :key 'car))
+             (group-info (gnus-get-info artgroup))
+             (marks (gnus-info-marks group-info))
+             (unread (gnus-uncompress-sequence
+                      (gnus-range-difference (gnus-active artgroup)
+                                             (gnus-info-read group-info)))))
+        (gnus-atomic-progn
+          (setf (gnus-info-read info)
+                (gnus-add-to-range
+                 (gnus-info-read info)
+                 (delq nil
+                       (mapcar
+                        #'(lambda (art)
+                            (unless (memq (cdr art) unread) (car art)))
+                        artids))))
+          (pcase-dolist (`(,type . ,range) marks)
+            (setq range (gnus-uncompress-sequence range))
+            (gnus-add-marked-articles
+             group type
+             (delq nil
+                   (mapcar
+                    #'(lambda (art)
+                        (when (memq (cdr art) range)
+                          (car art)))  artids)))))))
+    (gnus-set-active group (cons 1 (nnselect-artlist-length
+                                    gnus-newsgroup-selection)))))
+(deffoo nnselect-request-thread (header &optional group server)
+  (with-current-buffer gnus-summary-buffer
+    (let ((group (nnselect-add-prefix group))
+          ;; find the best group for the originating article. if its a
+          ;; pseudo-article look for real articles in the same thread
+          ;; and see where they come from.
+          (artgroup (nnselect-article-group
+                     (if (> (mail-header-number header) 0)
+                         (mail-header-number header)
+                       (if (> (gnus-summary-article-number) 0)
+                           (gnus-summary-article-number)
+                         (let ((thread
+                                (gnus-id-to-thread (mail-header-id header))))
+                           (when thread
+                             (cl-some #'(lambda (x)
+                                          (when (and x (> x 0)) x))
+                                      (gnus-articles-in-thread thread)))))))))
+      ;; Check if we are dealing with an imap backend.
+      (if (eq 'nnimap
+              (car (gnus-find-method-for-group artgroup)))
+          ;; If so we perform the query, massage the result, and return
+          ;; the new headers back to the caller to incorporate into the
+          ;; current summary buffer.
+          (let* ((group-spec
+                  (list (delq nil (list
+                                   (or server (gnus-group-server artgroup))
+                                   (unless  gnus-refer-thread-use-search
+                                     artgroup)))))
+                 (query-spec
+                  (list (cons 'query (nnimap-make-thread-query header))
+                        (cons 'criteria "")))
+                 (last (nnselect-artlist-length gnus-newsgroup-selection))
+                 (first (1+ last))
+                 (new-nnselect-artlist
+                  (nnir-run-query
+                   (list (cons 'nnir-query-spec query-spec)
+                         (cons 'nnir-group-spec group-spec))))
+                 old-arts seq
+                 headers)
+            (mapc
+             #'(lambda (article)
+                 (if
+                     (setq seq
+                           (cl-position article
+                                        gnus-newsgroup-selection :test 'equal))
+                     (push (1+ seq) old-arts)
+                   (setq gnus-newsgroup-selection
+                         (vconcat gnus-newsgroup-selection (vector article)))
+                   (cl-incf last)))
+             new-nnselect-artlist)
+            (setq headers
+                  (gnus-fetch-headers
+                   (append (sort old-arts '<)
+                           (number-sequence first last)) nil t))
+            (gnus-group-set-parameter
+             group
+             'nnselect-artlist
+             (nnselect-compress-artlist gnus-newsgroup-selection))
+            (when (>= last first)
+              (let (new-marks)
+                (pcase-dolist (`(,artgroup . ,artids)
+                               (ids-by-group (number-sequence first last)))
+                  (pcase-dolist (`(,type . ,marked)
+                                 (gnus-info-marks (gnus-get-info artgroup)))
+                    (setq marked (gnus-uncompress-sequence marked))
+                    (when (setq new-marks
+                                (delq nil
+                                      (mapcar
+                                       #'(lambda (art)
+                                           (when (memq (cdr art) marked)
+                                             (car art)))
+                                       artids)))
+                      (nconc
+                       (symbol-value
+                        (intern
+                         (format "gnus-newsgroup-%s"
+                                 (car (rassq type gnus-article-mark-lists)))))
+                       new-marks)))))
+              (setq gnus-newsgroup-active
+                    (cons 1 (nnselect-artlist-length gnus-newsgroup-selection)))
+              (gnus-set-active
+               group
+               (cons 1 (nnselect-artlist-length gnus-newsgroup-selection))))
+            headers)
+        ;; If not an imap backend just warp to the original article
+        ;; group and punt back to gnus-summary-refer-thread.
+        (and (gnus-warp-to-article) (gnus-summary-refer-thread))))))
+(deffoo nnselect-close-group (group &optional _server)
+  (let ((group (nnselect-add-prefix group)))
+    (unless gnus-group-is-exiting-without-update-p
+      (nnselect-push-info group))
+    (setq gnus-newsgroup-selection nil)
+    (when (gnus-ephemeral-group-p group)
+      (gnus-kill-ephemeral-group group)
+      (setq gnus-ephemeral-servers
+            (assq-delete-all 'nnselect gnus-ephemeral-servers)))))
+(deffoo nnselect-request-create-group (group &optional _server args)
+  (message "Creating nnselect group %s" group)
+  (let* ((group (gnus-group-prefixed-name  group '(nnselect "nnselect")))
+         (specs (assq 'nnselect-specs args))
+         (function-spec
+          (or  (alist-get 'nnselect-function specs)
+               (intern (completing-read "Function: " obarray #'functionp))))
+         (args-spec
+          (or  (alist-get 'nnselect-args specs)
+               (read-from-minibuffer "Args: " nil nil t nil "nil")))
+         (nnselect-specs (list (cons 'nnselect-function function-spec)
+                               (cons 'nnselect-args args-spec))))
+    (gnus-group-set-parameter group 'nnselect-specs nnselect-specs)
+    (gnus-group-set-parameter
+     group 'nnselect-artlist
+     (nnselect-compress-artlist (or  (alist-get 'nnselect-artlist args)
+         (nnselect-run nnselect-specs))))
+    (nnselect-request-update-info group (gnus-get-info group)))
+  t)
+(deffoo nnselect-request-type (_group &optional article)
+  (if (and (numberp article) (> article 0))
+      (gnus-request-type
+       (nnselect-article-group article) (nnselect-article-number article))
+    'unknown))
+(deffoo nnselect-request-post (&optional _server)
+  (if (not gnus-message-group-art)
+      (nnheader-report 'nnselect "Can't post to an nnselect group")
+    (gnus-request-post
+     (gnus-find-method-for-group
+      (nnselect-article-group (cdr gnus-message-group-art))))))
+(deffoo nnselect-request-rename-group (_group _new-name &optional _server)
+  t)
+(deffoo nnselect-request-scan (group _method)
+  (when (and group
+             (gnus-group-get-parameter  (nnselect-add-prefix group)
+                                        'nnselect-rescan t))
+    (nnselect-request-group-scan group)))
+(deffoo nnselect-request-group-scan (group &optional _server _info)
+  (let* ((group (nnselect-add-prefix group))
+         (artlist (nnselect-run
+                   (gnus-group-get-parameter group 'nnselect-specs t))))
+    (gnus-set-active group (cons 1 (nnselect-artlist-length
+                                    artlist)))
+    (gnus-group-set-parameter
+     group 'nnselect-artlist
+     (nnselect-compress-artlist artlist))))
+;; Add any undefined required backend functions
+;; (nnoo-define-skeleton nnselect)
+;;; Util Code:
+(defun gnus-nnselect-group-p (group)
+  "Say whether GROUP is nnselect or not."
+  (or (and (gnus-group-prefixed-p group)
+           (eq 'nnselect (car (gnus-find-method-for-group group))))
+      (eq 'nnselect (car gnus-command-method))))
+(defun nnselect-run (specs)
+  "Apply nnselect-function to nnselect-args from SPECS.
+Return an article list."
+  (let ((func (alist-get 'nnselect-function specs))
+        (args (alist-get 'nnselect-args specs)))
+    (funcall func args)))
+(defun nnselect-search-thread (header)
+  "Make an nnselect group containing the thread with article HEADER.
+The current server will be searched.  If the registry is
+installed, the server that the registry reports the current
+article came from is also searched."
+  (let* ((query
+          (list (cons 'query (nnimap-make-thread-query header))
+                (cons 'criteria "")))
+         (server
+          (list (list (gnus-method-to-server
+           (gnus-find-method-for-group gnus-newsgroup-name)))))
+         (registry-group (and
+                          (bound-and-true-p gnus-registry-enabled)
+                          (car (gnus-registry-get-id-key
+                                (mail-header-id header) 'group))))
+         (registry-server
+          (and registry-group
+               (gnus-method-to-server
+                (gnus-find-method-for-group registry-group)))))
+    (when registry-server (cl-pushnew (list registry-server) server
+                                      :test 'equal))
+    (gnus-group-read-ephemeral-group
+     (concat "nnselect-" (message-unique-id))
+     (list 'nnselect "nnselect")
+     nil
+     (cons (current-buffer) gnus-current-window-configuration)
+                                        ;     nil
+     nil nil
+     (list
+      (cons 'nnselect-specs
+            (list
+             (cons 'nnselect-function 'nnir-run-query)
+             (cons 'nnselect-args
+                   (list (cons 'nnir-query-spec query)
+                         (cons 'nnir-group-spec server)))))
+      (cons 'nnselect-artlist nil)))
+    (gnus-summary-goto-subject (gnus-id-to-article (mail-header-id header)))))
+(defun nnselect-push-info (group)
+  "Copy mark-lists from GROUP to the originating groups."
+  (let ((select-unreads (numbers-by-group gnus-newsgroup-unreads))
+        (select-reads (numbers-by-group
+                       (gnus-uncompress-range
+                        (gnus-info-read (gnus-get-info group)))))
+        (select-unseen (numbers-by-group gnus-newsgroup-unseen))
+        (gnus-newsgroup-active nil)
+        mark-list type-list)
+    (pcase-dolist (`(,mark . ,type) gnus-article-mark-lists)
+      (when (setq type-list
+                  (symbol-value (intern (format "gnus-newsgroup-%s" mark))))
+        (push (cons type
+                    (numbers-by-group
+                     (gnus-uncompress-range type-list))) mark-list)))
+    (pcase-dolist (`(,artgroup . ,artlist)
+                   (numbers-by-group gnus-newsgroup-articles))
+      (let* ((group-info (gnus-get-info artgroup))
+             (old-unread (gnus-list-of-unread-articles artgroup))
+             newmarked)
+        (when group-info
+          (pcase-dolist (`(,_mark . ,type) gnus-article-mark-lists)
+            (let ((select-type
+                   (sort
+                    (cdr (assoc artgroup  (alist-get type mark-list)))
+                    '<))  list)
+              (setq list
+                    (gnus-uncompress-range
+                     (gnus-add-to-range
+                      (gnus-remove-from-range
+                       (alist-get type (gnus-info-marks group-info))
+                       artlist)
+                      select-type)))
+              (when list
+                ;; Get rid of the entries of the articles that have the
+                ;; default score.
+                (when (and (eq type 'score)
+                           gnus-save-score
+                           list)
+                  (let* ((arts list)
+                         (prev (cons nil list))
+                         (all prev))
+                    (while arts
+                      (if (or (not (consp (car arts)))
+                              (= (cdar arts) gnus-summary-default-score))
+                          (setcdr prev (cdr arts))
+                        (setq prev arts))
+                      (setq arts (cdr arts)))
+                    (setq list (cdr all)))))
+              (when  (or (eq (gnus-article-mark-to-type type) 'list)
+                         (eq (gnus-article-mark-to-type type) 'range))
+                (setq list
+                      (gnus-compress-sequence  (sort list '<) t)))
+              ;; When exiting the group, everything that's previously been
+              ;; unseen is now seen.
+              (when (eq  type 'seen)
+                (setq list (gnus-range-add
+                            list (cdr (assoc artgroup select-unseen)))))
+              (when (or list (eq  type 'unexist))
+                (push (cons  type list) newmarked))))
+          (gnus-atomic-progn
+            ;; Enter these new marks into the info of the group.
+            (if (nthcdr 3 group-info)
+                (setcar (nthcdr 3 group-info) newmarked)
+              ;; Add the marks lists to the end of the info.
+              (when newmarked
+                (setcdr (nthcdr 2 group-info) (list newmarked))))
+            ;; Cut off the end of the info if there's nothing else there.
+            (let ((i 5))
+              (while (and (> i 2)
+                          (not (nth i group-info)))
+                (when (nthcdr (cl-decf i) group-info)
+                  (setcdr (nthcdr i group-info) nil))))
+            ;; update read and unread
+            (gnus-update-read-articles
+             artgroup
+             (gnus-uncompress-range
+              (gnus-add-to-range
+               (gnus-remove-from-range
+                old-unread
+                (cdr (assoc artgroup select-reads)))
+               (sort (cdr (assoc artgroup select-unreads)) '<))))
+            (gnus-get-unread-articles-in-group
+             group-info (gnus-active artgroup) t)
+            (gnus-group-update-group artgroup t t)))))))
+(declare-function gnus-registry-get-id-key "gnus-registry" (id key))
+(defun gnus-summary-make-search-group (nnir-extra-parms)
+  "Search a group from the summary buffer.
+Pass NNIR-EXTRA-PARMS on to the search engine."
+  (interactive "P")
+  (gnus-warp-to-article)
+  (let ((spec
+         (list
+          (cons 'nnir-group-spec
+                (list (list
+                       (gnus-group-server gnus-newsgroup-name)
+                       gnus-newsgroup-name))))))
+    (gnus-group-make-search-group nnir-extra-parms spec)))
+;; The end.
+(provide 'nnselect)
+;;; nnselect.el ends here
diff --git a/lisp/gnus/nnspool.el b/lisp/gnus/nnspool.el
index 33b68fa989e..0b6bba5fea7 100644
--- a/lisp/gnus/nnspool.el
+++ b/lisp/gnus/nnspool.el
@@ -422,7 +422,7 @@ there.")
             (nnspool-article-pathname nnspool-current-group article))
        (nnheader-insert-article-line article)
        (goto-char (point-min))
-        (let ((headers (nnheader-parse-head)))
+        (let ((headers (nnheader-parse-head nil t)))
          (set-buffer cur)
          (goto-char (point-max))
          (nnheader-insert-nov headers)))