anchor.diff:  
       start_seq,
       history,
  +    session_id,
       source_log,
       target_log,
       rep_starttime,
  
positive.code:     {SrcInstanceStartTime, TgtInstanceStartTime} ->
          ?LOG_INFO("recording a checkpoint for ~s -> ~s at source update_seq ~p",
              [dbname(Source), dbname(Target), NewSeqNum]),
          SessionId = couch_uuids:random(),
          NewHistoryEntry = {[
              {<<"session_id">>, SessionId},
              {<<"start_time">>, list_to_binary(ReplicationStartTime)},
  
negative.code: 
          start_seq = StartSeq,
          history = History,
          session_id = couch_uuids:random(),
          source_log = SourceLog,
          target_log = TargetLog,
          rep_starttime = httpd_util:rfc1123_date(),
  