On the 'move-tracking-2' branch: Add a basic test (or exercise, really) of
merging.

* subversion/tests/cmdline/svnmover_tests.py
  (merges): New test.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/move-tracking-2@1640192 13f79535-47bb-0310-9956-ffa450edef68