Please describe the problem:
Double click on modified file opens the file instead of showing the diff between
it and base version. This is caused by incorrect invocation of svn diff command. 
Is is called as "svn diff -u" but it seems that "-u" has different meaning in
svn (nothing to do with diff) and svn complains about bad options:

Subcommand 'diff' doesn't accept option '-u [--show-updates]'
Type 'svn help diff' for usage.

The svn version is:

$svn --version
svn, version 1.2.3 (r15833)
   compiled Oct 19 2005, 03:34:07

After removing the "-u" switch from svn.py module it seems all is working fine.
Here is the patch:

diff -u svn.py svn.py.orig
--- svn.py      2005-11-18 10:06:42.160326520 +0200
+++ svn.py.orig 2005-11-18 10:06:31.834896224 +0200
@@ -39,7 +39,7 @@
     def commit_command(self, message):
         return [self.CMD,"commit","-m",message]
     def diff_command(self):
-        return [self.CMD,"diff"]
+        return [self.CMD,"diff","-u"]
     def update_command(self):
         return [self.CMD,"update"]
     def add_command(self, binary=0):


Steps to reproduce:
1. Open svn directory
2. Double click on Modified file

Actual results:
View file contents.

Expected results:
View diff between file and its base version.

Does this happen every time?
Yes.

Other information: