As kpreid on #svn kindly points out, if you need to make a patch for a subversion project that includes files you have created, you need to add the files:

svn add tests/fixtures/empty.rb

Then you can run svn diff > my_patch.diff, and everything will be included.

Anyone can add files to their working copy, it’s just that they can’t necessarily commit them.

This ought to be in their FAQ.