bug#21649: 25.0.50; [PATCH] Allow M-x man to reuse an existing window

[Nicolas Richard]

When running M-x man RET man RET, then C-x o to select the newly created
window and then running M-x man RET sed RET, what you get is: two "man"
windows side by side. It would make sense to re-use the existing one.

How to best do that I do not know. If modifying the code is necessary,
here's an attempt at adding an option in Man-notify-method. (I'm not
attached to this implementation, and even less attached to the silly
name `manly' that I chose, btw.)

>From 2b812b1c9f91af2cf6116f1d4e334154ae44c724 Mon Sep 17 00:00:00 2001
From: Nicolas Richard <youngfrog@members.fsf.org>
Date: Thu, 8 Oct 2015 10:50:07 +0200
Subject: [PATCH] Allow M-x man to reuse an existing window

* man.el (Man-notify-when-ready): add `manly' option.
(Man-notify-method): augment docstring accordingly.
---
 lisp/man.el | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/lisp/man.el b/lisp/man.el
index c5dbcba..a02ee79 100644
--- a/lisp/man.el
+++ b/lisp/man.el
@@ -91,6 +91,8 @@
 (require 'ansi-color)
 (require 'cl-lib)
 (require 'button)
+(require 'subr-x)
+(require 'seq)
 
 (defgroup man nil
   "Browse UNIX manual pages."
@@ -162,6 +164,8 @@ (defcustom Man-notify-method (if (boundp 'Man-notify) 
Man-notify 'friendly)
 bully      -- make the manpage the current buffer and only window (sf)
 aggressive -- make the manpage the current buffer in the other window (sf)
 friendly   -- display manpage in the other window but don't make current (sf)
+manly      -- like `friendly' but re-use a window displaying a man page if
+              possible (sf)
 polite     -- don't display manpage, but prints message and beep when ready
 quiet      -- like `polite', but don't beep
 meek       -- make no indication that the manpage is ready
@@ -1166,6 +1170,16 @@ (defun Man-notify-when-ready (man-buffer)
        (and (frame-live-p saved-frame)
             (select-frame saved-frame))
        (display-buffer man-buffer 'not-this-window))
+      (`manly
+       (and (frame-live-p saved-frame)
+            (select-frame saved-frame))
+       (if-let ((window (seq-some-p
+                         (lambda (window)
+                           (with-current-buffer (window-buffer window)
+                             (derived-mode-p 'Man-mode)))
+                         (window-list))))
+           (set-window-buffer window man-buffer)
+         (display-buffer man-buffer)))
       (`polite
        (beep)
        (message "Manual buffer %s is ready" (buffer-name man-buffer)))
-- 
2.4.6