[patch] describe-variable mention :version and :package-version info

[John Paul Wallington]

I don't think `describe-variable' is sufficiently gnarly or long
enough yet.  Is it okay to install the following change?

2007-10-19  John Paul Wallington  <address@hidden>

        * help-fns.el (describe-variable): Note customizable variable's
        version or package version.

diff -ub

--- help-fns.el 16 Oct 2007 17:35:41 +0100      1.105
+++ help-fns.el 19 Oct 2007 23:50:57 +0100      
@@ -643,7 +643,7 @@
              (with-current-buffer standard-output
                (insert (or doc "Not documented as a variable."))))
            ;; Make a link to customize if this variable can be customized.
-           (if (custom-variable-p variable)
+           (when (custom-variable-p variable)
                (let ((customize-label "customize"))
                  (terpri)
                  (terpri)
@@ -652,7 +652,32 @@
                    (save-excursion
                      (re-search-backward
                       (concat "\\(" customize-label "\\)") nil t)
-                     (help-xref-button 1 'help-customize-variable variable)))))
+                   (help-xref-button 1 'help-customize-variable variable))))
+             ;; Add a note for variable with version or package version
+             (let ((custom-version (get variable 'custom-version))
+                   (cpv (get variable 'custom-package-version))
+                   (output nil))
+               (if custom-version
+                   (setq output 
+                         (format "This variable was introduced, or its default 
value was changed, in\nversion %s of Emacs.\n"
+                                 custom-version))
+                 (when cpv
+                   (let* ((package (car-safe cpv))
+                          (version (car (cdr-safe cpv)))
+                          (pkg-versions (assq package 
customize-package-emacs-version-alist))
+                          (emacsv (cdr (assoc version pkg-versions))))
+                     (if (and package version)
+                         (setq output
+                               (format (concat "This variable was introduced, 
or its default value was changed, in\nversion %s of the %s package"           
+                                               (if emacsv
+                                                   (format " that is part of 
Emacs %s" emacsv))
+                                               ".\n")
+                                       version package))))))
+               (when output
+                 (terpri)
+                 (terpri)
+                 (princ output))))
+           
            (print-help-return-message)
            (save-excursion
              (set-buffer standard-output)