Add a regression test for 'svn diff --properties-only'.
Add a regression test for 'svn diff --properties-only'.

* subversion/tests/cmdline/diff_tests.py
  (diff_properties_only, test_list): New test.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion