Unity documentation has a brief page on the subject.
- Follow the above instructions & create a repo for your Unity project in svn.
- Once you have your local Working Copy set up & opened in the Unity IDE, Unity will generate a Library folder next to your Assets.
- DO NOT ever version the Library folder. Leave it unversioned. If you’re using an SVN client like Cornerstone on OS X, select the Library folder, Ctrl+click it & choose Ignore. This way you’ll never have to see those files popup in the Unversioned view or accidentally include them in a Commit. If you’re using command line, set Library to be ignored via Terminal, as you probably already know how.