Index: subversion/svn/diff-cmd.c
===================================================================
--- subversion/svn/diff-cmd.c	(revision 17595)
+++ subversion/svn/diff-cmd.c	(working copy)
@@ -152,9 +152,18 @@
         }
 
       if (url_present && working_copy_present)
-        return svn_error_createf (SVN_ERR_UNSUPPORTED_FEATURE, NULL,
-                                  _("Target lists to diff may not contain "
-                                    "both working copy paths and URLs"));
+        {
+          /* Create a two-line error message.  The message appearing
+             first here appears last in the output.  */
+          svn_error_t *err
+            = (svn_error_createf
+               (SVN_ERR_UNSUPPORTED_FEATURE, NULL,
+                _("Consider using the '--old' and '--new' options")));
+          return (svn_error_createf
+                  (SVN_ERR_UNSUPPORTED_FEATURE, err,
+                   _("Target lists to diff may not contain "
+                     "both working copy paths and URLs")));
+        }
           
       if (opt_state->start_revision.kind == svn_opt_revision_unspecified
           && working_copy_present)