# File lib/librarian/puppet/source/git.rb, line 8
        def hash_from(remote, reference)
          branch_names = remote_branch_names[remote]
          if branch_names.include?(reference)
            reference = "#{remote}/#{reference}"
          end

          command = ??(rev-parse #{reference}^{commit} --quiet)
          run!(command, :chdir => true).strip
        end