This section is from the "Version Control with Subversion" book, by Ben Collins-Sussman, Brian W. Fitzpatrick and C. Michael Pilato. Also available from Amazon: Version Control with Subversion.
We've already seen svn diff before—it displays file differences in unified diff format; it was used to show the local modifications made to our working copy before committing to the repository.
In fact, it turns out that there are three distinct uses of svn diff:
Examining local changes
Comparing your working copy to the repository
Comparing repository to repository