I just ran into a fascinating configuration where someone is doing Subversion checkouts on top of existing Subversion checkouts. I'd never even *THOUGHT* of pulling such a stunt, but it's apparently workable.
I'm concerned, though, that any change in the source of the Subversion checkout to a branch or tag will simply break things, or any reloaction of the source repository component will also break things. I'm also concerned that, should someone mix and match components inside the working copy manually, things will break in fascinating fashion, or that locally modified components will only be updated, not actually replaced. Has anyone been using this feature? It seems to work to do an "svn checkout" on top of an existing working copy of the same URL or earlier releases, but I've not tried rolling back the revision number or other games. I could spend a bunch of time checkout out border cases, but would welcome insights.