(rmail-duplicate-message): Make it work.

[gnu-emacs] / lisp / vc.el

diff --git a/lisp/vc.el b/lisp/vc.el
index 865a4018eb154819b059b5b4d20055e9588a8cea..e9de682285ae6348a00af18a86a86cb4c103e099 100644 (file)
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -1,7 +1,7 @@
 ;;; vc.el --- drive a version-control system from within Emacs
 
 ;; Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 2000,
-;;   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
+;;   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
 ;;   Free Software Foundation, Inc.
 
 ;; Author:     FSF (see below for full credits)
@@ -697,16 +697,17 @@ These are passed to the checkin program by \\[vc-register]."
 
 (defcustom vc-diff-switches nil
   "A string or list of strings specifying switches for diff under VC.
-When running diff under a given BACKEND, VC concatenates the values of
-`diff-switches', `vc-diff-switches', and `vc-BACKEND-diff-switches' to
-get the switches for that command.  Thus, `vc-diff-switches' should
-contain switches that are specific to version control, but not
-specific to any particular backend."
-  :type '(choice (const :tag "None" nil)
+When running diff under a given BACKEND, VC uses the first
+non-nil value of `vc-BACKEND-diff-switches', `vc-diff-switches',
+and `diff-switches', in that order.  Since nil means to check the
+next variable in the sequence, either of the first two may use
+the value t to mean no switches at all.  `vc-diff-switches'
+should contain switches that are specific to version control, but
+not specific to any particular backend."
+  :type '(choice (const :tag "Unspecified" nil)
+                (const :tag "None" t)
                 (string :tag "Argument String")
-                (repeat :tag "Argument List"
-                        :value ("")
-                        string))
+                (repeat :tag "Argument List" :value ("") string))
   :group 'vc
   :version "21.1")