def get_version(node, group, oid)
      repo, path = yield_repo_and_path(node, group)
      repo = Git.open repo
      unlock repo
      repo.gtree(oid).files[path].contents
    rescue StandardError
      'version not found'
    ensure
      lock repo
    end
def get_version(node, group, oid)
      repo, path = yield_repo_and_path(node, group)
      repo = Git.open repo
      unlock repo
      repo.gtree(oid).files[path].contents
    rescue StandardError
      'version not found'
    ensure
      lock repo
    end
give the blob of a specific revision