In the diff tests, factor out the presentation of diff headers and property diffs into helper functions.
In the diff tests, factor out the presentation of diff headers and property
diffs into helper functions.

* subversion/tests/cmdline/diff_tests.py
  (make_diff_prop_header, make_diff_prop_deleted, make_diff_prop_added,
   make_diff_prop_modified): New functions.
  (diff_only_property_change, diff_property_changes_to_base,
   diff_prop_change_local_propmod, diff_repos_wc_add_with_props,
   diff_with_depth, diff_prop_missing_context, diff_prop_multiple_hunks,
   diff_git_with_props, diff_correct_wc_base_revnum,
   diff_git_with_props_on_dir): Use them.

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