code: func upsertIntent(intents map[string]nodeIntent, node string, itype messageType,
  	ltime LamportTime, stamper func() time.Time) bool {
  	if intent, ok := intents[node]; !ok || ltime > intent.LTime {
  		intents[node] = nodeIntent{
  			Type:     itype,
  			WallTime: stamper(),
  			LTime:    ltime,
  		}
  		return true
  	}
  
  	return false
  }
docs: // upsertIntent will update an existing intent with the supplied Lamport time,
  // or create a new entry. This will return true if a new entry was added. The
  // stamper is used to capture the wall clock time for expiring these buffered
  // intents. Make sure the memberLock is held when passing in the Serf instance's
  // recentIntents member.