# File lib/rugged_adapter/git_layer_rugged.rb, line 251
      def ref_to_sha(query)
        return query if sha?(query)
        query = "refs/heads/#{query}" if !query.nil? && !(query =~ /^refs\/heads\//) && !(query == "HEAD")
        begin
          return @repo.rev_parse_oid(query)
        rescue Rugged::ReferenceError, Rugged::InvalidError
          return nil
        end
      end