anchor.diff:              let rec loop (cache : ExpiringDictionary<XUri, int>) = async {
                   let! msg = inbox.Receive()
                   cache.Set(msg, 0, mergeabilityTTL)
  +                logger.DebugFormat("Queued '{0}' for mergeability check in '{1}'", msg, mergeTTL)
                   return! loop cache
               }
               loop(cache)
  
positive.code:     let GITHUB_API = Plug.New(new XUri("https://api.github.com"))
      let DATE_PATTERN = "yyyyMMdd"
      let logger = LogManager.GetLogger typedefof<PullRequestService>
  
      // Supervisor agent
      let supervisor =
  
negative.code:             let rec loop (cache : ExpiringDictionary<XUri, int>) = async {
                  let! msg = inbox.Receive()
                  cache.Set(msg, 0, mergeTTL)
                  logger.DebugFormat("Queued '{0}' for merge in '{1}'", msg, mergeTTL)
                  return! loop cache
              }
              loop(cache)
  
      // Polling agent
      let pollAgent =
          let cache = new ExpiringDictionary<XUri, int>(timerFactory, false)
          cache.EntryExpired.Add <|
              fun args ->
                  let prUri, retry = args.Entry.Key, args.Entry.Value
  