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