(vc-svn-diff-switches): Don't default to vc-diff-switches.

diff --git a/lisp/vc-svn.el b/lisp/vc-svn.el
index 46d83685475f4c6e196e4f9408075dace869a3e0..1d46c90d9c86942188dbbf7e517b83e8e00b2c04 100644 (file)
--- a/lisp/vc-svn.el
+++ b/lisp/vc-svn.el
@@ -65,9 +65,13 @@ A string or list of strings passed to the checkin program by
   :version "21.4"
   :group 'vc)
 
-(defcustom vc-svn-diff-switches nil
-  "*A string or list of strings specifying extra switches for svn diff under VC."
-    :type '(choice (const :tag "None" nil)
+(defcustom vc-svn-diff-switches
+  t                       ;`svn' doesn't support common args like -c or -b.
+  "String or list of strings specifying extra switches for svn diff under VC.
+If nil, use the value of `vc-diff-switches'.
+If you want to force an empty list of arguments, use t."
+  :type '(choice (const :tag "Unspecified" nil)
+                (const :tag "None" t)
                 (string :tag "Argument String")
                 (repeat :tag "Argument List"
                         :value ("")