When you decide to move a svn repository to the public it might be necessary to remove older versions from history.
For example, lets say your repository is at version 10000. However up until version 9000 you where not considering going open source. But once you did you cleaned up the code. However the old dirty code is still in svn history.
You don’t want to lose all of the history, just everything below version 9000.
This is how you do it.
svnadmin dump /path/to/current/repo -r9000:10000 > svn.dump
svnadmin create /path/to/new/repo
svnadmin load /path/to/new/repo < svn.dump
Poof! Version 9000 and below are gone. The repository is now at version 1000.