Expand the tests for 'svnsync' stripping r0 from mergeinfo, following theembarrassing bug introduced in r1646250 and fixed in r1656893.The approach taken here also moves the test case data from the dumpfiles tothe Python test code which arguably makes it easier to read.* subversion/tests/cmdline/svnsync_tests_data/mergeinfo-contains-r0.dump Reduce this to a stub.* subversion/tests/cmdline/svnsync_tests_data/mergeinfo-contains-r0.expected.dump Delete.* subversion/tests/cmdline/svnsync_tests.py (mergeinfo_contains_r0): Create the input and expected dumpfile contents by constructing node records containing mergeinfo and appending them to the dumpfile stub. Add test cases where no change is expected, and more thorough test cases where a change is expected.