I made the mistake of creating a Subversion repository without the usual trunk, branches, and tags directories. That is, the root dire
The easiest way would be to create a 'trunk' directory, then move everything else into it. You'll have to copy any properties manually, but it shouldn't be a big deal. The history is per-file, so it should remain.
The other issue to consider is whether anybody else has the repository open. It'll be difficult to merge, so make sure everyone has their changes checked in before you do this.