Add a major-mode for the *Messages* buffer

Ref: http://lists.gnu.org/archive/html/emacs-devel/2010-02/msg00135.html

* lisp/simple.el (messages-buffer-mode): New major mode.
(messages-buffer): New function.

* lisp/startup.el (normal-top-level): Switch mode of *Messages* buffer.

* src/xdisp.c (message_dolog): If we create *Messages*,
switch it to messages-buffer-mode.

* lisp/emacs-lisp/ert.el (ert--force-message-log-buffer-truncation)
(ert-run-test): Use `message-buffer' function.
(ert--force-message-log-buffer-truncation): Ignore read-only.

* lisp/help.el (view-echo-area-messages): Use `message-buffer' function.

* lisp/mail/emacsbug.el (report-emacs-bug): Use `message-buffer' function.

* lisp/gnus/gnus-util.el (gnus-message-with-timestamp-1):
Use `message-buffer' function if available.  Ignore read-only.

* etc/NEWS: Mention this.

8 files changed, 47 insertions, 16 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 15afc3ad19e..ceae81b91e0 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,14 @@
+2013-09-17  Glenn Morris  <rgm@gnu.org>
+
+	* simple.el (messages-buffer-mode): New major mode.
+	(messages-buffer): New function.
+	* startup.el (normal-top-level): Switch mode of *Messages* buffer.
+	* emacs-lisp/ert.el (ert--force-message-log-buffer-truncation)
+	(ert-run-test): Use `message-buffer' function.
+	(ert--force-message-log-buffer-truncation): Ignore read-only.
+	* help.el (view-echo-area-messages): Use `message-buffer' function.
+	* mail/emacsbug.el (report-emacs-bug): Use `message-buffer' function.
+
 2013-09-17  Stefan Monnier  <monnier@iro.umontreal.ca>
 
 	* subr.el (eval-after-load): Preserve evaluation order (bug#15389).
diff --git a/lisp/emacs-lisp/ert.el b/lisp/emacs-lisp/ert.el
index 98576687f3d..409e4faf4d5 100644
--- a/lisp/emacs-lisp/ert.el
+++ b/lisp/emacs-lisp/ert.el
@@ -785,7 +785,7 @@ This mainly sets up debugger-related bindings."
   "Immediately truncate *Messages* buffer according to `message-log-max'.
 
 This can be useful after reducing the value of `message-log-max'."
-  (with-current-buffer (get-buffer-create "*Messages*")
+  (with-current-buffer (messages-buffer)
     ;; This is a reimplementation of this part of message_dolog() in xdisp.c:
     ;; if (NATNUMP (Vmessage_log_max))
     ;;   {
@@ -798,7 +798,8 @@ This can be useful after reducing the value of `message-log-max'."
             (end (save-excursion
                    (goto-char (point-max))
                    (forward-line (- message-log-max))
-                   (point))))
+                   (point)))
+            (inhibit-read-only t))
         (delete-region begin end)))))
 
 (defvar ert--running-tests nil
@@ -818,7 +819,7 @@ Returns the result and stores it in ERT-TEST's `most-recent-result' slot."
   (setf (ert-test-most-recent-result ert-test) nil)
   (cl-block error
     (let ((begin-marker
-           (with-current-buffer (get-buffer-create "*Messages*")
+           (with-current-buffer (messages-buffer)
              (point-max-marker))))
       (unwind-protect
           (let ((info (make-ert--test-execution-info
@@ -837,7 +838,7 @@ Returns the result and stores it in ERT-TEST's `most-recent-result' slot."
                   (ert--run-test-internal info))
               (let ((result (ert--test-execution-info-result info)))
                 (setf (ert-test-result-messages result)
-                      (with-current-buffer (get-buffer-create "*Messages*")
+                      (with-current-buffer (messages-buffer)
                         (buffer-substring begin-marker (point-max))))
                 (ert--force-message-log-buffer-truncation)
                 (setq should-form-accu (nreverse should-form-accu))
diff --git a/lisp/gnus/ChangeLog b/lisp/gnus/ChangeLog
index fc8ff9fd695..2889ead69ed 100644
--- a/lisp/gnus/ChangeLog
+++ b/lisp/gnus/ChangeLog
@@ -1,3 +1,8 @@
+2013-09-17  Glenn Morris  <rgm@gnu.org>
+
+	* gnus-util.el (gnus-message-with-timestamp-1):
+	Use `message-buffer' function if available.  Ignore read-only.
+
 2013-09-16  Katsumi Yamaoka  <yamaoka@jpl.org>
 
 	* message.el (message-expand-group, message-completion-in-region):
diff --git a/lisp/gnus/gnus-util.el b/lisp/gnus/gnus-util.el
index 1d2ab2da248..4f63f4bdbc0 100644
--- a/lisp/gnus/gnus-util.el
+++ b/lisp/gnus/gnus-util.el
@@ -514,11 +514,14 @@ but also to the ones displayed in the echo area."
 			     (> message-log-max 0)
 			     (/= (length str) 0))
 		    (setq time (current-time))
-		    (with-current-buffer (get-buffer-create "*Messages*")
+		    (with-current-buffer (if (fboundp 'messages-buffer)
+					     (messages-buffer)
+					   (get-buffer-create "*Messages*"))
 		      (goto-char (point-max))
-		      (insert ,timestamp str "\n")
-		      (forward-line (- message-log-max))
-		      (delete-region (point-min) (point))
+		      (let ((inhibit-read-only t))
+			(insert ,timestamp str "\n")
+			(forward-line (- message-log-max))
+			(delete-region (point-min) (point)))
 		      (goto-char (point-max))))
 		  str)
 		 (gnus-add-timestamp-to-message
diff --git a/lisp/help.el b/lisp/help.el
index 4ec0b99a593..c21d5b8c1d1 100644
--- a/lisp/help.el
+++ b/lisp/help.el
@@ -1,7 +1,6 @@
 ;;; help.el --- help commands for Emacs
 
-;; Copyright (C) 1985-1986, 1993-1994, 1998-2013 Free Software
-;; Foundation, Inc.
+;; Copyright (C) 1985-1986, 1993-1994, 1998-2013 Free Software Foundation, Inc.
 
 ;; Maintainer: FSF
 ;; Keywords: help, internal
@@ -412,7 +411,7 @@ With argument, display info only for the selected version."
 The number of messages retained in that buffer
 is specified by the variable `message-log-max'."
   (interactive)
-  (with-current-buffer (get-buffer-create "*Messages*")
+  (with-current-buffer (messages-buffer)
     (goto-char (point-max))
     (display-buffer (current-buffer))))
 
diff --git a/lisp/mail/emacsbug.el b/lisp/mail/emacsbug.el
index c1bc7e2e1ab..e045519e850 100644
--- a/lisp/mail/emacsbug.el
+++ b/lisp/mail/emacsbug.el
@@ -1,7 +1,7 @@
 ;;; emacsbug.el --- command to report Emacs bugs to appropriate mailing list
 
-;; Copyright (C) 1985, 1994, 1997-1998, 2000-2013 Free Software
-;; Foundation, Inc.
+;; Copyright (C) 1985, 1994, 1997-1998, 2000-2013
+;;   Free Software Foundation, Inc.
 
 ;; Author: K. Shane Hartman
 ;; Maintainer: FSF
@@ -160,7 +160,7 @@ Prompts for bug subject.  Leaves you in a mail buffer."
 			     (report-emacs-bug-can-use-osx-open)))
         user-point message-end-point)
     (setq message-end-point
-	  (with-current-buffer (get-buffer-create "*Messages*")
+	  (with-current-buffer (messages-buffer)
 	    (point-max-marker)))
     (compose-mail report-emacs-bug-address topic)
     ;; The rest of this does not execute if the user was asked to
diff --git a/lisp/simple.el b/lisp/simple.el
index 593f36d1ee1..54630681a68 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -7344,6 +7344,18 @@ and setting it to nil."
 	 buffer-invisibility-spec)
     (setq buffer-invisibility-spec nil)))
 
+(define-derived-mode messages-buffer-mode special-mode "Messages"
+  "Major mode used in the \"*Messages*\" buffer.")
+
+(defun messages-buffer ()
+  "Return the \"*Messages*\" buffer.
+If it does not exist, create and it switch it to `messages-buffer-mode'."
+  (or (get-buffer "*Messages*")
+      (with-current-buffer (get-buffer-create "*Messages*")
+        (messages-buffer-mode)
+        (current-buffer))))
+
+
 ;; Minibuffer prompt stuff.
 
 ;;(defun minibuffer-prompt-modification (start end)
diff --git a/lisp/startup.el b/lisp/startup.el
index ec7d73306a2..059d7710320 100644
--- a/lisp/startup.el
+++ b/lisp/startup.el
@@ -1,7 +1,6 @@
 ;;; startup.el --- process Emacs shell arguments  -*- lexical-binding: t -*-
 
-;; Copyright (C) 1985-1986, 1992, 1994-2013 Free Software Foundation,
-;; Inc.
+;; Copyright (C) 1985-1986, 1992, 1994-2013 Free Software Foundation, Inc.
 
 ;; Maintainer: FSF
 ;; Keywords: internal
@@ -494,6 +493,7 @@ It is the default value of the variable `top-level'."
     (setq command-line-processed t)
     (let ((dir default-directory))
       (with-current-buffer "*Messages*"
+        (messages-buffer-mode)
         ;; Make it easy to do like "tail -f".
         (set (make-local-variable 'window-point-insertion-type) t)
         ;; Give *Messages* the same default-directory as *scratch*,