Accessing the doxygen files in a subversion repository

I don't think this is necessary. Manually maintaining the documentation like this is not ideal and takes a lot of time. Try this method instead:

1. On the machine hosting Subversion/Trac, checkout the repository that you are interested in documenting into a local working directory.
2. Create a post-commit script that updates the above working directory and generates the Doxygen documentation (in the background, if possible).

Because the documentation will be generated when the commit is successful, you can be sure that you are always serving the latest/greatest documentation.

Instead of a post-commit hook I use Bitten and the following build recipe to generate the latest doxygen documentation and then rsync's them to the SVN host at a location the DoxygenPlugin for Trac is configured to look.

<build xmlns:svn="http://bitten.cmlenz.net/tools/svn"
       xmlns:sh="http://bitten.cmlenz.net/tools/sh">
  <step id="checkout" description="Checkout source from repository">
    <svn:checkout url="https://svn/project/"
        path="${path}" revision="${revision}" />
  </step>
  <step id="build" description="Compile">
    <sh:exec executable="doxygen" args=".doxyfile" /> 
  </step>
  <step id="rsync" description="Update Trac Doxygen">
    <sh:exec executable="rsync" args="-rvz --delete /var/local/doxygen/project/ svn@svn:/var/local/doxygen/project" /> 
  </step>
</build>