subversion: merge without a working copy

I want to revert a bad commit from command-line svn. The usual advice is to reverse merge the commit into your working copy and then commit the changes. In my case, the bad commit was a mis-typed svn import which trashed a portion of my repository I don't have checked out anywhere else. I could check out the affected directories and then follow the usual advice, but it would be more elegant if I could reverse-merge entirely using URLs, without a working copy. Is this possible?