* lisp/files.el (revert-buffer-function): Use a non-nil default.

(revert-buffer-preserve-modes): Declare var to
provide access to the `preserve-modes' argument.
(revert-buffer): Let-bind it.
(revert-buffer--default): New function, extracted from revert-buffer.

2 files changed, 124 insertions, 108 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 4c115d8435a..24fbe1acb2c 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,13 @@
 2013-07-24  Stefan Monnier  <monnier@iro.umontreal.ca>
 
+        * files.el (revert-buffer-function): Use a non-nil default.
+        (revert-buffer-preserve-modes): Declare var to
+        provide access to the `preserve-modes' argument.
+        (revert-buffer): Let-bind it.
+        (revert-buffer--default): New function, extracted from revert-buffer.
+
+2013-07-24  Stefan Monnier  <monnier@iro.umontreal.ca>
+
         * lpr.el: Signal print errors more prominently.
         (print-region-function): Don't default to nil.
         (lpr-print-region): New function, extracted from print-region-1.
diff --git a/lisp/files.el b/lisp/files.el
index ff4ccec2279..10d66e0b2e0 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -5246,10 +5246,12 @@ comparison."
 
 
 (put 'revert-buffer-function 'permanent-local t)
-(defvar revert-buffer-function nil
+(defvar revert-buffer-function #'revert-buffer--default
   "Function to use to revert this buffer, or nil to do the default.
 The function receives two arguments IGNORE-AUTO and NOCONFIRM,
-which are the arguments that `revert-buffer' received.")
+which are the arguments that `revert-buffer' received.
+It also has access to the `preserve-modes' argument of `revert-buffer'
+via the `revert-buffer-preserve-modes' dynamic variable.")
 
 (put 'revert-buffer-insert-file-contents-function 'permanent-local t)
 (defvar revert-buffer-insert-file-contents-function nil
@@ -5296,6 +5298,11 @@ This is true even if a `revert-buffer-function' is being used.")
 
 (defvar revert-buffer-internal-hook)
 
+;; `revert-buffer-function' was defined long ago to be a function of only
+;; 2 arguments, so we have to use a dynbind variable to pass the
+;; `preserve-modes' argument of `revert-buffer'.
+(defvar revert-buffer-preserve-modes)
+
 (defun revert-buffer (&optional ignore-auto noconfirm preserve-modes)
   "Replace current buffer text with the text of the visited file on disk.
 This undoes all changes since the file was visited or saved.
@@ -5337,112 +5344,113 @@ non-nil, it is called instead of rereading visited file contents."
   ;; reversal of the argument sense.  So I'm just changing the user
   ;; interface, but leaving the programmatic interface the same.
   (interactive (list (not current-prefix-arg)))
-  (if revert-buffer-function
-      (let ((revert-buffer-in-progress-p t))
-        (funcall revert-buffer-function ignore-auto noconfirm))
-    (with-current-buffer (or (buffer-base-buffer (current-buffer))
-                             (current-buffer))
-      (let* ((revert-buffer-in-progress-p t)
-             (auto-save-p (and (not ignore-auto)
-                               (recent-auto-save-p)
-                               buffer-auto-save-file-name
-                               (file-readable-p buffer-auto-save-file-name)
-                               (y-or-n-p
-     "Buffer has been auto-saved recently.  Revert from auto-save file? ")))
-             (file-name (if auto-save-p
-                            buffer-auto-save-file-name
-                          buffer-file-name)))
-        (cond ((null file-name)
-               (error "Buffer does not seem to be associated with any file"))
-              ((or noconfirm
-                   (and (not (buffer-modified-p))
-                        (catch 'found
-                          (dolist (regexp revert-without-query)
-                            (when (string-match regexp file-name)
-                              (throw 'found t)))))
-                   (yes-or-no-p (format "Revert buffer from file %s? "
-                                        file-name)))
-               (run-hooks 'before-revert-hook)
-               ;; If file was backed up but has changed since,
-               ;; we should make another backup.
-               (and (not auto-save-p)
-                    (not (verify-visited-file-modtime (current-buffer)))
-                    (setq buffer-backed-up nil))
-               ;; Effectively copy the after-revert-hook status,
-               ;; since after-find-file will clobber it.
-               (let ((global-hook (default-value 'after-revert-hook))
-                     (local-hook (when (local-variable-p 'after-revert-hook)
-                                   after-revert-hook))
-                     (inhibit-read-only t))
-                 (cond
-                  (revert-buffer-insert-file-contents-function
-                   (unless (eq buffer-undo-list t)
-                     ;; Get rid of all undo records for this buffer.
-                     (setq buffer-undo-list nil))
-                   ;; Don't make undo records for the reversion.
-                   (let ((buffer-undo-list t))
-                     (funcall revert-buffer-insert-file-contents-function
-                              file-name auto-save-p)))
-                  ((not (file-exists-p file-name))
-                   (error (if buffer-file-number
-                              "File %s no longer exists!"
-                            "Cannot revert nonexistent file %s")
-                          file-name))
-                  ((not (file-readable-p file-name))
-                   (error (if buffer-file-number
-                              "File %s no longer readable!"
-                            "Cannot revert unreadable file %s")
-                          file-name))
-                  (t
-                   ;; Bind buffer-file-name to nil
-                   ;; so that we don't try to lock the file.
-                   (let ((buffer-file-name nil))
-                     (or auto-save-p
-                         (unlock-buffer)))
-                   (widen)
-                   (let ((coding-system-for-read
-                          ;; Auto-saved file should be read by Emacs's
-                          ;; internal coding.
-                          (if auto-save-p 'auto-save-coding
-                            (or coding-system-for-read
-                                (and
-                                 buffer-file-coding-system-explicit
-                                 (car buffer-file-coding-system-explicit))))))
-                     (if (and (not enable-multibyte-characters)
-                              coding-system-for-read
-                              (not (memq (coding-system-base
-                                          coding-system-for-read)
-                                         '(no-conversion raw-text))))
-                         ;; As a coding system suitable for multibyte
-                         ;; buffer is specified, make the current
-                         ;; buffer multibyte.
-                         (set-buffer-multibyte t))
-
-                     ;; This force after-insert-file-set-coding
-                     ;; (called from insert-file-contents) to set
-                     ;; buffer-file-coding-system to a proper value.
-                     (kill-local-variable 'buffer-file-coding-system)
-
-                     ;; Note that this preserves point in an intelligent way.
-                     (if preserve-modes
-                         (let ((buffer-file-format buffer-file-format))
-                           (insert-file-contents file-name (not auto-save-p)
-                                                 nil nil t))
-                       (insert-file-contents file-name (not auto-save-p)
-                                             nil nil t)))))
-                 ;; Recompute the truename in case changes in symlinks
-                 ;; have changed the truename.
-                 (setq buffer-file-truename
-                       (abbreviate-file-name (file-truename buffer-file-name)))
-                 (after-find-file nil nil t nil preserve-modes)
-                 ;; Run after-revert-hook as it was before we reverted.
-                 (setq-default revert-buffer-internal-hook global-hook)
-                 (if local-hook
-                     (set (make-local-variable 'revert-buffer-internal-hook)
-                          local-hook)
-                   (kill-local-variable 'revert-buffer-internal-hook))
-                 (run-hooks 'revert-buffer-internal-hook))
-               t))))))
+  (let ((revert-buffer-in-progress-p t)
+        (revert-buffer-preserve-modes preserve-modes))
+    (funcall (or revert-buffer-function #'revert-buffer--default)
+             ignore-auto noconfirm)))
+(defun revert-buffer--default (ignore-auto noconfirm)
+  (with-current-buffer (or (buffer-base-buffer (current-buffer))
+                           (current-buffer))
+    (let* ((auto-save-p (and (not ignore-auto)
+                             (recent-auto-save-p)
+                             buffer-auto-save-file-name
+                             (file-readable-p buffer-auto-save-file-name)
+                             (y-or-n-p
+                              "Buffer has been auto-saved recently.  Revert from auto-save file? ")))
+           (file-name (if auto-save-p
+                          buffer-auto-save-file-name
+                        buffer-file-name)))
+      (cond ((null file-name)
+             (error "Buffer does not seem to be associated with any file"))
+            ((or noconfirm
+                 (and (not (buffer-modified-p))
+                      (catch 'found
+                        (dolist (regexp revert-without-query)
+                          (when (string-match regexp file-name)
+                            (throw 'found t)))))
+                 (yes-or-no-p (format "Revert buffer from file %s? "
+                                      file-name)))
+             (run-hooks 'before-revert-hook)
+             ;; If file was backed up but has changed since,
+             ;; we should make another backup.
+             (and (not auto-save-p)
+                  (not (verify-visited-file-modtime (current-buffer)))
+                  (setq buffer-backed-up nil))
+             ;; Effectively copy the after-revert-hook status,
+             ;; since after-find-file will clobber it.
+             (let ((global-hook (default-value 'after-revert-hook))
+                   (local-hook (when (local-variable-p 'after-revert-hook)
+                                 after-revert-hook))
+                   (inhibit-read-only t))
+               (cond
+                (revert-buffer-insert-file-contents-function
+                 (unless (eq buffer-undo-list t)
+                   ;; Get rid of all undo records for this buffer.
+                   (setq buffer-undo-list nil))
+                 ;; Don't make undo records for the reversion.
+                 (let ((buffer-undo-list t))
+                   (funcall revert-buffer-insert-file-contents-function
+                            file-name auto-save-p)))
+                ((not (file-exists-p file-name))
+                 (error (if buffer-file-number
+                            "File %s no longer exists!"
+                          "Cannot revert nonexistent file %s")
+                        file-name))
+                ((not (file-readable-p file-name))
+                 (error (if buffer-file-number
+                            "File %s no longer readable!"
+                          "Cannot revert unreadable file %s")
+                        file-name))
+                (t
+                 ;; Bind buffer-file-name to nil
+                 ;; so that we don't try to lock the file.
+                 (let ((buffer-file-name nil))
+                   (or auto-save-p
+                       (unlock-buffer)))
+                 (widen)
+                 (let ((coding-system-for-read
+                        ;; Auto-saved file should be read by Emacs's
+                        ;; internal coding.
+                        (if auto-save-p 'auto-save-coding
+                          (or coding-system-for-read
+                              (and
+                               buffer-file-coding-system-explicit
+                               (car buffer-file-coding-system-explicit))))))
+                   (if (and (not enable-multibyte-characters)
+                            coding-system-for-read
+                            (not (memq (coding-system-base
+                                        coding-system-for-read)
+                                       '(no-conversion raw-text))))
+                       ;; As a coding system suitable for multibyte
+                       ;; buffer is specified, make the current
+                       ;; buffer multibyte.
+                       (set-buffer-multibyte t))
+
+                   ;; This force after-insert-file-set-coding
+                   ;; (called from insert-file-contents) to set
+                   ;; buffer-file-coding-system to a proper value.
+                   (kill-local-variable 'buffer-file-coding-system)
+
+                   ;; Note that this preserves point in an intelligent way.
+                   (if revert-buffer-preserve-modes
+                       (let ((buffer-file-format buffer-file-format))
+                         (insert-file-contents file-name (not auto-save-p)
+                                               nil nil t))
+                     (insert-file-contents file-name (not auto-save-p)
+                                           nil nil t)))))
+               ;; Recompute the truename in case changes in symlinks
+               ;; have changed the truename.
+               (setq buffer-file-truename
+                     (abbreviate-file-name (file-truename buffer-file-name)))
+               (after-find-file nil nil t nil revert-buffer-preserve-modes)
+               ;; Run after-revert-hook as it was before we reverted.
+               (setq-default revert-buffer-internal-hook global-hook)
+               (if local-hook
+                   (set (make-local-variable 'revert-buffer-internal-hook)
+                        local-hook)
+                 (kill-local-variable 'revert-buffer-internal-hook))
+               (run-hooks 'revert-buffer-internal-hook))
+             t)))))
 
 (defun recover-this-file ()
   "Recover the visited file--get contents from its last auto-save file."