svn diff of working copy file to unrelated branch file

Here is the scenario:

User 1
   1. create branches/X
   2. svn checkout branches/X to local machine
   3. modify file.txt
   4. commit changes

Another user, User 2,
   5. create branches/Y
   6. svn checkout branches/Y to his local machine
   7. merge branches/X to local machine (and thus merges file.txt into
branches/Y)
   8. use svn diff to verify that the changes to file.txt in the local
copy of branches/Y succeeded before committing the change.

Since svn diff can not compare the local working copy to that of a URL,
this is impossible to do without first committing the change to
branches/Y.
But this defeats the whole purpose of verifying that a merge has produced
the correct results before committing the merge changes.

I have googled for this, but have not found any usable solution.
Only recommended solution is to check out branches/X so that svn can
compare two paths.
Since the merge changes have not been checked in yet, I can not use svn
diff with two URL's.

It is impractical, not to mention time consuming and tedious, to checkout
both branches/X and branches/Y just so that I can perform a diff.

Joneric Wennerstrom / Sr Programmer/Anlyst-Specialized Systems /
Engineering & Factory Systems Support
MS 188-400, 221 3rd Ave SE , Cedar Rapids, IA, 52401, USA
Phone: 319-263-4597 / Fax: 319-263-6067
jwenners_at_rockwellcollins.com
www.rockwellcollins.com