[Old patch] Unify fn and var help to make learning elisp a little easier

[Kelly Dean]

I originally proposed this a couple years ago:
https://lists.gnu.org/archive/html/emacs-devel/2012-12/msg00165.html

At the time, my patch was declined due to a paperwork issue. However, the FSF 
now has a disclaimer on file for me, so that issue has been solved.

I've been using this patch since the time I wrote it, and find it handy. I 
rarely use «C-h v» or «C-h f» anymore.

If other people might find it useful too, I propose installing it in Emacs. 
Stefan and Drew suggested maybe using a different keybinding than «C-h o», 
though. (I'll have to re-train my muscle memory, but that's ok.) The remaining 
lowercase options for «C-h» are [juxyz]. Of those, I would vote for x.

A copy of my original patch is attached below.

--- emacs-24.2/lisp/help-fns.el
+++ emacs-24.2/lisp/help-fns.el
@@ -897,6 +897,37 @@
 
 
 ;;;###autoload
+(defun describe-function-or-variable (symbol &optional buffer frame)
+  "Display the full documentation of the function or variable SYMBOL.
+If SYMBOL is a variable and has a buffer-local value in BUFFER or FRAME
+\(default to the current buffer and current frame), it is displayed along
+with the global value."
+  (interactive
+   (let* ((v-or-f (variable-at-point))
+        (found (symbolp v-or-f))
+        (v-or-f (if found v-or-f (function-called-at-point)))
+        (found (or found v-or-f))
+        (enable-recursive-minibuffers t)
+        val)
+     (setq val (completing-read (if found
+                                   (format
+                                    "Describe function or variable (default 
%s): " v-or-f)
+                                 "Describe function or variable: ")
+                               obarray
+                               (lambda (vv)
+                                 (or (fboundp vv)
+                                     (get vv 'variable-documentation)
+                                     (and (boundp vv) (not (keywordp vv)))))
+                               t nil nil
+                               (if found (symbol-name v-or-f))))
+     (list (if (equal val "")
+              v-or-f (intern val)))))
+  (if (not (symbolp symbol)) (message "You didn't specify a function or 
variable")
+    (unless (buffer-live-p buffer) (setq buffer (current-buffer)))
+    (unless (frame-live-p frame) (setq frame (selected-frame)))
+    (help-xref-interned symbol buffer frame)))
+
+;;;###autoload
 (defun describe-syntax (&optional buffer)
   "Describe the syntax specifications in the syntax table of BUFFER.
 The descriptions are inserted in a help buffer, which is then displayed.
--- emacs-24.2/lisp/help-mode.el
+++ emacs-24.2/lisp/help-mode.el
@@ -627,10 +627,13 @@
 
 
 ;; Additional functions for (re-)creating types of help buffers.
-(defun help-xref-interned (symbol)
+
+;;;###autoload
+(defun help-xref-interned (symbol &optional buffer frame)
   "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
 Both variable, function and face documentation are extracted into a single
-help buffer."
+help buffer. If SYMBOL is a variable, include buffer-local value for optional
+BUFFER or FRAME."
   (with-current-buffer (help-buffer)
     ;; Push the previous item on the stack before clobbering the output buffer.
     (help-setup-xref nil nil)
@@ -646,7 +649,7 @@
                          (get symbol 'variable-documentation))
                  ;; Don't record the current entry in the stack.
                  (setq help-xref-stack-item nil)
-                 (describe-variable symbol))))
+                 (describe-variable symbol buffer frame))))
       (cond
        (sdoc
        ;; We now have a help buffer on the variable.
--- emacs-24.2/lisp/help.el
+++ emacs-24.2/lisp/help.el
@@ -90,6 +90,7 @@
     (define-key map "k" 'describe-key)
     (define-key map "l" 'view-lossage)
     (define-key map "m" 'describe-mode)
+    (define-key map "o" 'describe-function-or-variable)
     (define-key map "n" 'view-emacs-news)
     (define-key map "p" 'finder-by-keyword)
     (define-key map "P" 'describe-package)
@@ -215,6 +216,7 @@
 m           Display documentation of current minor modes and current major 
mode,
               including their special commands.
 n           Display news of recent Emacs changes.
+o SYMBOL    Display the given function or variable's documentation and value.
 p TOPIC     Find packages matching a given topic keyword.
 r           Display the Emacs manual in Info mode.
 s           Display contents of current syntax table, plus explanations.