[PATCH] View Differences before saving

[Mario Lang]

Hello Emacsers :)

I've just received the confirmation that my
past and future changes assigment arrived
at the FSF.  So I prepared a slightly
improved version of my previos patch (thanks Kim)
for submittion.  I don't have CVS access, so if
the patch looks OK and is accepted that way, I'd like
to ask someone with CVS access to install it.

Here's the ChangeLog entry:

2002-08-20  Mario Lang  <address@hidden>

            * files.el: (diff-buffer-with-file): New function.
            Intended for save-some-buffers-action-alist, but
            useful in general.
            * (save-some-buffers): Removed static
            data in call to map-y-or-n-p and moved into
            save-some-buffers-action-alist.
            * save-some-buffers-action-alist: New variable.
            Added option `d' using diff-buffer-to-file.
 

And here is the patch:

Index: files.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/files.el,v
retrieving revision 1.601
diff -u -r1.601 files.el
--- files.el    15 Aug 2002 20:08:24 -0000      1.601
+++ files.el    20 Aug 2002 13:15:01 -0000
@@ -2992,17 +2992,64 @@
                 (rename-file (cdr setmodes) buffer-file-name))))))
     setmodes))
 
+(defun diff-buffer-with-file (&optional buffer)
+  "View the differences between BUFFER and its associated file.
+This requires the external program \"diff\" to be in your `exec-path'."
+  (interactive "bBuffer: ")
+  (setq buffer (get-buffer (or buffer (current-buffer))))
+  (let ((buf-filename (buffer-file-name buffer)))
+    (unless buf-filename
+      (error "Buffer %s has no associated file" buffer))
+    (let ((diff-buf (get-buffer-create "*Buffer-diff*")))
+      (with-current-buffer buffer
+       (save-restriction
+         (widen)
+         (if (zerop
+              (shell-command-on-region (point-min) (point-max)
+               (concat "diff "
+                       (when (and (boundp 'ediff-custom-diff-options)
+                                  (stringp ediff-custom-diff-options))
+                         ediff-custom-diff-options)
+                       " " buf-filename " -") diff-buf))
+             (message "No differences found")
+           (progn
+             (with-current-buffer diff-buf
+               (goto-char (point-min))
+               (if (fboundp 'diff-mode)
+                   (diff-mode)
+                 (fundamental-mode)))
+             (display-buffer diff-buf))))))
+    nil))
+
+(defvar save-some-buffers-action-alist
+  '((?\C-r
+     (lambda (buf)
+       (view-buffer buf
+                   (lambda (ignore)
+                     (exit-recursive-edit)))
+       (recursive-edit)
+       ;; Return nil to ask about BUF again.
+       nil)
+     "display the current buffer")
+    (?d #'diff-buffer-with-file
+       "Show difference to last saved version"))
+  "ACTION-ALIST argument used in call to `map-y-or-n-p'.")
+
 (defun save-some-buffers (&optional arg pred)
   "Save some modified file-visiting buffers.  Asks user about each one.
-You can answer `y' to save, `n' not to save, or `C-r' to look at the
-buffer in question with `view-buffer' before deciding.
+You can answer `y' to save, `n' not to save, `C-r' to look at the
+buffer in question with `view-buffer' before deciding or `d' to
+view the differences using `diff-buffer-to-file'.
 
 Optional argument (the prefix) non-nil means save all with no questions.
 Optional second argument PRED determines which buffers are considered:
 If PRED is nil, all the file-visiting buffers are considered.
 If PRED is t, then certain non-file buffers will also be considered.
 If PRED is a zero-argument function, it indicates for each buffer whether
-to consider it or not when called with that buffer current."
+to consider it or not when called with that buffer current.
+
+See `save-some-buffers-action-alist' if you want to
+change the additional actions you can take on files."
   (interactive "P")
   (save-window-excursion
     (let* ((queried nil)
@@ -3034,15 +3081,7 @@
                (save-buffer)))
             (buffer-list)
             '("buffer" "buffers" "save")
-            (list (list ?\C-r (lambda (buf)
-                                (view-buffer buf
-                                             (function
-                                              (lambda (ignore)
-                                                (exit-recursive-edit))))
-                                (recursive-edit)
-                                ;; Return nil to ask about BUF again.
-                                nil)
-                        "display the current buffer"))))
+            save-some-buffers-action-alist))
           (abbrevs-done
            (and save-abbrevs abbrevs-changed
                 (progn

-- 
CYa,
  Mario