Subversion diff patching wasn't implemented very well. svn patch

almost always returns a 0 exit code, even if nothing is applied or

conflicts are found. Because of this, we'd claim a patch applied

successfully even if it didn't. We also didn't include information on

conflicts, and we had string type issues for empty files.
This fixes all of this, and adds unit tests (except for empty files,

which will be covered in an upcoming change).
We now parse the output of svn patch to determine whether anything was

applied and whether anything had conflicts, returning those details in

the PatchResult.
We also now patch empty files correctly, by fixing the string type

issues.
Unit tests have been fully fleshed out for most of this.

Unit tests pass.