Mark vc-dir-show-outgoing-count obsolete

* lisp/vc/vc-dir.el (vc-dir-show-outgoing-count): Mark obsolete.
(vc-dir-async-header-values): Use a list of cons.
(vc-dir-headers, vc-dir-refresh): Update for new
vc-dir-async-header-values structure.
* doc/emacs/maintaining.texi (VC Directory Buffer): Delete
mention of the variable.
* etc/NEWS: Announce the obsoletion.

doc/emacs/maintaining.texi

@@ -1599,17 +1599,6 @@ unpushed revisions"} where @var{N} is a number.  You can click on this
 text to execute the @code{vc-root-log-outgoing} command (@pxref{VC
 Change Log}).
 
-@vindex vc-dir-show-outgoing-count
-  Emacs tries to use cached information to determine the number of
-unpushed revisions, but for some backends this isn't possible.  In these
-cases Emacs must occasionally fetch from the remote repository in order
-to determine the count.  If your connection to the remote repository is
-slow then this may cause unacceptable slowdowns in refreshing the VC
-Directory buffer.  If this affects you, you can customize
-@code{vc-dir-show-outgoing-count} to @code{nil} to disable the unpushed
-revisions count altogether.  You can also set this on a per-repository
-basis using directory local variables (@pxref{Directory Variables}).
-
 @node VC Directory Commands
 @subsubsection VC Directory Commands
 

etc/NEWS

@@ -80,6 +80,14 @@ is a symbolic link to 'target/', then 'C-x v d link/ RET' is the same as
 the project root is a symbolic link, 'C-x p v' first finds the truename
 of the directory named by that link, and then opens VC-Dir there.
 
+** VC
+
++++
+*** VC-Dir outgoing revisions count is now asynchronous.
+This means it won't get in your way even if it's slow for your
+repository.  As such, the 'vc-dir-show-outgoing-count' option is now
+obsolete.
+
 
 * New Modes and Packages in Emacs 32.1
 

lisp/vc/vc-dir.el

@@ -1414,15 +1414,14 @@ the *vc-dir* buffer.
 
 (defcustom vc-dir-show-outgoing-count t
   "Whether to display the number of unpushed revisions in VC-Dir.
-For some combinations of VC backends and remotes, determining how many
-outgoing revisions there are is slow, because the backend must fetch
-from the remote, and your connection to the remote is slow.  Customize
-this variable to nil to disable calculating the outgoing count and
-therefore also disable the fetching."
+This variable was for when the number of unpushed revisions was counted
+synchronously.  As that is now done asynchronously, this toggle is no
+longer needed."
   :type 'boolean
   :safe #'booleanp
   :group 'vc
   :version "31.1")
+(make-obsolete-variable 'vc-dir-show-outgoing-count nil "32.1")
 
 (defvar log-view-message-re)
 
@@ -1471,12 +1470,9 @@ uses OVERLAY."
                (kill-buffer buf))))))
 
 (defvar-local vc-dir-async-header-values
-  '((vc-dir-show-outgoing-count "Outgoing" vc-dir--count-outgoing))
+  '(("Outgoing" . vc-dir--count-outgoing))
   "List of specifications for asynchronously computed VC-Dir header values.
-Each element is a list (VAR HEADER FUN) where
-- VAR is the name of a variable.
-  If the variable's value is nil, the async header will not be included.
-  This is so the user can turn off including the header.
+Each element is a pair (HEADER . FUN) where
 - HEADER is a string label for the header in the VC-Dir buffer.
 - FUN is a function of two arguments (BACKEND OVERLAY) that starts the
   asynchronous computation of the header's value.  BACKEND is the VC
@@ -1507,11 +1503,10 @@ specific headers."
                'face 'vc-dir-header-value)
    (vc-call-backend backend 'dir-extra-headers dir)
    "\n"
-   (mapconcat (pcase-lambda (`(,var ,header ,_))
-                (and (symbol-value var)
-                     (concat (propertize (format "%-11s: " header)
-                                         'face 'vc-dir-header)
-                             "\n")))
+   (mapconcat (pcase-lambda (`(,header . ,_))
+                (concat (propertize (format "%-11s: " header)
+                                    'face 'vc-dir-header)
+                        "\n"))
               vc-dir-async-header-values)))
 
 (defun vc-dir-refresh-files (files)
@@ -1605,7 +1600,7 @@ Throw an error if another update process is in progress."
         (delete-overlay overlay))
       ;; Set up new async header overlays.
       (save-excursion
-        (pcase-dolist (`(,_ ,field ,fun) vc-dir-async-header-values)
+        (pcase-dolist (`(,field . ,fun) vc-dir-async-header-values)
           (goto-char (point-min))
           (when (re-search-forward (format "^%s\\s-" field) nil t)
             (funcall fun backend (make-overlay (pos-eol) (pos-eol))))))