RFR: vcs: make RepositoryTests deterministic

[Erik Helin]

Hi all,

please review this small patch to make the test `RepositoryTests.testCommitMetadataWithBranchesWithGit` deterministic. The problem is that different versions of `git` can traverse the commit graph differently and the resulting list from the call to `commitMetadataFor` might therefore contain commits in an unknown order. The test should therefore not assume that the commits are ordered in a particular way, but instead ensure that the list contains only the expected commits.

Thanks,
Erik

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Commit messages:
 - vcs: make RepositoryTests deterministic

Changes: https://git.openjdk.java.net/skara/pull/1061/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1061&range=00
  Stats: 7 lines in 1 file changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/skara/pull/1061.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1061/head:pull/1061

PR: https://git.openjdk.java.net/skara/pull/1061