If you are caught somewhere between subversion 1.4  and 1.5 then you’ll suddenly find yourself one day presented with the message: 

svn: This client is too old to work with working copy; please get a newer Subversion client

I originally found myself here while beta testing a new subversion client and inadvertently clicking “yes” I want to upgrade my working directory. But that’s another story. Here’s what I did (I’m running Mac OSX 10.5 Leopard):

1. Download and install the Subversion 1.5 binaries from OpenCollabNet (via http://subversion.tigris.org/getting.html#osx). Once you download the .dmg, simply run the installer like you’d normally do any installer. You’d imagine that this would be all but it’s not because the new subversion installs to /opt/subversion/bin rather than /usr/bin.
2. Update your path by either editing the “~/.profile” (for your individual user profile) or “/etc/profile” (for all system users). I chose to do this for my system as I used several accounts for different purposes. If the file doesn’t exist you need to create it. Then add the following line to the top of the file: 

   export PATH=/opt/subversion:$PATH

3. Finally, rename the previous svn executable. You may find that you still cannot access subversion 1.5 if the 1.4 file is still available. Navigate to your /usr/bin folder and rename the old svn located there:

   $sudo mv svn svn.old

   • Thanks much Coals [2] Newcastle for helping me with this one. 
4. Now when running svn –version you should see the 1.5 client referenced.

$ svn –version
svn, version 1.5.2 (r32768)
   compiled Sep 19 2008, 14:38:15
Copyright (C) 2000-2008 CollabNet.
Subversion is open source software, see http://subversion.tigris.org/
This product includes software developed by CollabNet (http://www.Collab.Net/).