GNU bug report logs - #5225
dired-diff should be more safe

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From: bug-gnu-emacs <at> gnu.org (Emacs bug Tracking System)
To: Juri Linkov <juri <at> jurta.org>
Subject: bug#5225 closed by Juri Linkov <juri <at> jurta.org> (Re: bug#5225:
 dired-diff should be more safe)
Date: Fri, 18 Dec 2009 07:33:03 +0000

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This is an automatic notification regarding your bug report
which was filed against the emacs package:

#5225: dired-diff should be more safe

It has been closed by Juri Linkov <juri <at> jurta.org>.

Their explanation is attached below along with your original report.
If this explanation is unsatisfactory and you have not received a
better one in a separate message then please contact Juri Linkov <juri <at> jurta.org> by
replying to this email.


-- 
5225: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=5225
Emacs Bug Tracking System
Contact bug-gnu-emacs <at> gnu.org with problems

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From: Juri Linkov <juri <at> jurta.org>
To: 5225-done <at> debbugs.gnu.org
Subject: Re: bug#5225: dired-diff should be more safe
Date: Thu, 17 Dec 2009 03:19:27 +0200

Fixed.

-- 
Juri Linkov
http://www.jurta.org/emacs/

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From: Juri Linkov <juri <at> jurta.org>
To: emacs-pretest-bug <at> gnu.org
Subject: dired-diff should be more safe
Date: Wed, 16 Dec 2009 11:19:09 +0200

Currently using `dired-diff' has a high risk of deleting a file.

When two compared file names refer to the same file, or when one of them
is the directory name of the second file (thus the file is compared
against itself), then the user may not notice that `diff' compares the
same file with itself, and when `diff' says there are no differences,
decide to delete the file (thinking that two files have the same content).

The patch below eliminates this risk by signalling an error when
comparing the same file to itself:

=== modified file 'lisp/dired-aux.el'
--- lisp/dired-aux.el	2009-11-25 17:15:19 +0000
+++ lisp/dired-aux.el	2009-12-16 09:16:34 +0000
@@ -60,27 +60,44 @@
 		       (if (stringp diff-switches)
 			   diff-switches
 			 (mapconcat 'identity diff-switches " ")))))))
-  (diff file (dired-get-filename t) switches))
+  (let ((current (dired-get-filename t)))
+    (when (or (equal (expand-file-name file)
+		     (expand-file-name current))
+	      (and (file-directory-p file)
+		   (equal (expand-file-name current file)
+			  (expand-file-name current))))
+      (error "Attempt to compare the file to itself"))
+    (diff file current switches)))
 
 ;;;###autoload
 (defun dired-backup-diff (&optional switches)

-- 
Juri Linkov
http://www.jurta.org/emacs/

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