* files.el (revert-buffer): Do not discard undo list when buffer
        cannot be reverted because file does not exist.

*** files.el	Wed Feb  1 10:17:44 2006
--- files.el	Tue Feb  7 10:32:00 2006
***************
*** 3815,3821 ****
  			       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)))
--- 3815,3821 ----
  			       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)))
***************
*** 3840,3845 ****
--- 3840,3848 ----
  		    (setq buffer-backed-up nil))
  	       ;; Get rid of all undo records for this buffer.
  	       (or (eq buffer-undo-list t)
+ 		   ;; Do not clear buffer-undo-list if reverting will fail.
+ 		   (and (not (file-readable-p file-name))
+ 			(not revert-buffer-insert-file-contents-function))
  		   (setq buffer-undo-list nil))
  	       ;; Effectively copy the after-revert-hook status,
  	       ;; since after-find-file will clobber it.
***************
*** 3847,3863 ****
  		     (local-hook-p (local-variable-p 'after-revert-hook))
  		     (local-hook (and (local-variable-p 'after-revert-hook)
  				      after-revert-hook)))
! 		 (let (buffer-read-only
! 		       ;; Don't make undo records for the reversion.
! 		       (buffer-undo-list t))
! 		   (if revert-buffer-insert-file-contents-function
! 		       (funcall revert-buffer-insert-file-contents-function
! 				file-name auto-save-p)
! 		     (if (not (file-exists-p file-name))
! 			 (error (if buffer-file-number
! 				    "File %s no longer exists!"
! 				  "Cannot revert nonexistent file %s")
! 				file-name))
  		     ;; Bind buffer-file-name to nil
  		     ;; so that we don't try to lock the file.
  		     (let ((buffer-file-name nil))
--- 3850,3876 ----
  		     (local-hook-p (local-variable-p 'after-revert-hook))
  		     (local-hook (and (local-variable-p 'after-revert-hook)
  				      after-revert-hook)))
! 		 (cond
! 		  (revert-buffer-insert-file-contents-function
! 		   (let (buffer-read-only
! 			 ;; Don't make undo records for the reversion.
! 			 (buffer-undo-list t))
! 		     (funcall revert-buffer-insert-file-contents-function
! 			      file-name auto-save-p)))
! 		  ;; Don't bind buffer-undo-list around the error reporting
! 		  ;; clauses to avoid that undo information gets lost when
! 		  ;; calling the debugger.
! 		  ((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 "File %s is not readable" file-name))
! 		  (t
! 		   (let (buffer-read-only
! 			 ;; Don't make undo records for the reversion.
! 			 (buffer-undo-list t))
  		     ;; Bind buffer-file-name to nil
  		     ;; so that we don't try to lock the file.
  		     (let ((buffer-file-name nil))
***************
*** 3865,3871 ****
  			   (unlock-buffer)))
  		     (widen)
  		     (let ((coding-system-for-read
! 			    ;; Auto-saved file shoule be read by Emacs'
  			    ;; internal coding.
  			    (if auto-save-p 'auto-save-coding
  			      (or coding-system-for-read
--- 3878,3884 ----
  			   (unlock-buffer)))
  		     (widen)
  		     (let ((coding-system-for-read
! 			    ;; Auto-saved file should be read by Emacs'
  			    ;; internal coding.
  			    (if auto-save-p 'auto-save-coding
  			      (or coding-system-for-read
***************
*** 3881,3887 ****
  			     (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
--- 3894,3900 ----
  			     (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