Add basic test coverage for the Subversion parser
Summary:
Ref T4327. Adds the same basic battery of tests to the SVN parser as the other parsers have.
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Test Plan:
Ran unit tests against SVN change parsing.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T4327
Differential Revision: https://secure.phabricator.com/D8016