dw: The patch supplied doesn't simply patch the existing functionality.  It
addresses the underlying approach to parsing the svn entries file, making it
more robust and resilient to changes.  It also doesn't explicitly require a
specific version number in the entries file.  It still checks the version, and
logs a warning if it is unaware of the version, but it will continue to function
even if the version is unknown (assuming any format changes are still compatible).

And to re-iterate my message from 2009-04-14, it does not make since to simply
shell out to svn.  While this approach is simple and would be straightforward in
some environments, it is non-trivial in general and creates a hard dependency on
a specific implementation of svn.  Some environments may be using another SVN
client, or may not have an SVN client at all (consider a folder mounted from
another system).  Furthermore, if the svn command is not in the user's path,
this further complicates the use of shelling out to svn (where to find the
binary, which binary to use, etc).

So for optimum compatibility and minimum dependencies, setuptools should
continue to have a pure-python means to determine the SVN info.

Furthermore, the patch as supplied makes it much easier to implement new
approaches for handling SVN entries.  So if one was to implement an approach
that shells out to svn, that approach could be implemented using the constructs
supplied by this patch.

I would consider adding 'svn info' support, but it would be wise to first commit
this tested implementation to address the immediate issue, and then we can
consider a subsequent patch per your suggestion.