I've been looking into various ways to do this.
The first way would to get the revision number is the way philjones suggests above. It may also be better to grab the next number on the list, which I believe is the latest committed revision. This would helpful for tags and branches. If
you're building a tagged branch, you probably are more interested in the latest revision of that tag, rather than latest revision of the repository, which will likely be completely different.
The second and third option are both using command line tools: "svn.exe info" and "svnversion.exe" These are both part of the subversion package, and could probably be bundled without too much fuss. Of course, it would still
mean relying on an external tool which isn't very desirable.
Another option is to use SVNSharp http://sharpsvn.open.collab.net/, however I believe its just a .Net wrapper around the command line tools. If that's the case (I need to do a little more research), it would probably be overkill to bring in.
So this first option seems the most attractive as it would be the most lightweight. However, I'd like to find out for sure if this "entries" file format is dependable and consistent for everyone. I imagine the SVN folks would prefer
we use their tools or API, but I don't know that for sure.