; * lisp/dired-aux.el (dired-diff): Fix TOCTOU, simplify.

diff --git a/lisp/dired-aux.el b/lisp/dired-aux.el
index 2b716b0b5b6c23b29c1cbb302def3d4dda09e0e0..98a8f35819975341cd423a55d5ccef42268b3c68 100644 (file)
--- a/lisp/dired-aux.el
+++ b/lisp/dired-aux.el
@@ -185,8 +185,8 @@ substituted, and will be passed through normally to the shell.
     proceed))
 
 ;;;###autoload
-(defun dired-diff (file &optional switches)
-  "Compare file at point with FILE using `diff'.
+(defun dired-diff (file &optional switches current)
+  "Compare CURRENT file with FILE using `diff'.
 If called interactively, prompt for FILE.
 If the mark is active in Transient Mark mode, use the file at the mark
 as the default for FILE.  (That's the mark set by \\[set-mark-command],
@@ -253,30 +253,19 @@ the string of command switches used as the third argument of `diff'."
                        ;; `M-n' candidates.
                        (file-backup-file-names current))
                      (dired-dwim-target-defaults (list current) target-dir))))
+     (when default (push (expand-file-name default) defaults))
      (list
-      (minibuffer-with-setup-hook
-         (lambda ()
-            (setq-local minibuffer-default-add-function nil)
-           (setq minibuffer-default defaults))
-       (read-file-name (format-prompt "Diff %s with" default current)
-                       target-dir default t))
+      (read-file-name (format-prompt "Diff %s with" defaults current)
+                     target-dir defaults t)
       (if current-prefix-arg
          (read-string "Options for diff: "
                       (if (stringp diff-switches)
                           diff-switches
-                        (mapconcat #'identity diff-switches " "))))))
+                        (mapconcat #'identity diff-switches " "))))
+      current))
    dired-mode)
-  (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"))
-    (if (and (backup-file-name-p current)
-            (equal file (file-name-sans-versions current)))
-       (diff current file switches)
-      (diff file current switches))))
+  (setq current (or current (dired-get-filename t)))
+  (diff file current switches))
 
 ;;;###autoload
 (defun dired-backup-diff (&optional switches)