Allow Gitaly tests to run against Git with SHA256
Supporting Git 256 is going to be a long road, though it would be great to allow the test suite to be executed with Git using the SHA256 function to hash objects. This would than in turn allow to iterate through the test suite and fix tests. The job might not need to run on each MR, as nightly is probably enough to gather the data on failures. Until the test suite is stable it could be moved.
epic