Extend the test that checks a merge aborts in the right way when conflicts
are raised.

The reason for being so thorough with this particular test is because I am
currently refactoring the way the merge handles a conflict, so I want good
test coverage.

(The new helper functions at the beginning of this patch are here placed
just before the test itself, but could better be moved to somewhere more
generally accessible.  The new expected_merge_output2() should probably be
combined with the existing expected_merge_output().)

* subversion/tests/cmdline/merge_tests.py
  (parse_changes_list, parse_rev_args,
   RangeList, expected_merge_output2, expected_out_and_err,
   check_mergeinfo, simple_merge): New functions.
  (conflict_aborted_mergeinfo_described): Test many more combinations:
    merges that raise a conflict during the first or last sub-range of the
    first or last specified range; both forward and reverse merges.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1444291 13f79535-47bb-0310-9956-ffa450edef68