We have code in SVNClient for adding empty hunk info to added/deleted

empty files, instead of just providing Index: lines, but this never

had any test coverage.
To ensure we have proper Subversion diff coverage, this change adds

missing unit tests for diffs and patching, covering both the added and

deleted files.
This required a new commit in the test Subversion repository, adding an

empty file we could delete for these tests.

Unit tests pass.