More tweaks to merge tests for *even* more types of empty rev range elision.
More tweaks to merge tests for *even* more types of empty rev range elision.

Follow-up to r25300.

* subversion/tests/cmdline/merge_tests.py
  (empty_rev_range_mergeinfo): Test the many flavors of empty revision range
  elision not previously tested.  Also test elision of merge info to the
  repository.

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