There are two things you can do:
- Check out a new clean working directory. No reason why you can't. Advantage, it doesn't touch your stuff.
- Revert your changes after you do an update. That will get you a clean checkout, but you will lose all of your changes.
Normally, you want to keep the changes you did and merge them back into the changes others have done. If you need a clean checkout, checkout a new working directory. That's the easiest and it keeps your changes. If you don't want your changes, revert them, run svn status
to verify you have no changes in the working copy (or nonversioned files), and then do an update. It will be a bit faster than a new clean checkout.