Say an unanswered merge check in its own words, with no action it cannot take (issue 438)

mesh-delivery now says a head whose merge check started and never answered as a
stalled line in state unanswered. Through the generic delivery words it would read
as a delivery and offer a Stop that mesh-delivery refuses, since no delivery of
the head exists; it now names the checks waited on and what the operator can do.

cmd/mesh-controller/plain_words.go

@@ -828,6 +828,9 @@ func stalledWords(l stalledLine, o conditions.Observation) (headline, explanatio
 				"to check it: the forge never announced it. It cannot merge until it is checked.", pull, long),
 			fmt.Sprintf("%s has a merge check now, or is closed", pull), needs, nil
 	}
+	if l.State == "unanswered" {
+		return unansweredWords(l, o)
+	}
 	held := l.State
 	if held == "" {
 		held = "held"
@@ -857,6 +860,38 @@ func stalledWords(l stalledLine, o conditions.Observation) (headline, explanatio
 		fmt.Sprintf("Delivery of %s is no longer %s", name, held), needs, actions
 }
 
+// unansweredWords are the plain words of a pull request's head whose merge check was asked and has not answered
+// within its bound (novox/hq issue 438): mesh-delivery holds no delivery of it, so there is nothing to stop, release
+// or close, and no action is offered. The operator's acts are a new commit, which asks the check again, or a look
+// at the build seat's queue, where a check that never ran may still wait.
+func unansweredWords(l stalledLine, o conditions.Observation) (headline, explanation, resolved, needs string,
+	actions []conditions.Action) {
+	repository, _, _ := strings.Cut(l.ID, "@")
+	pull := "A pull request of " + repoName(repository)
+	if l.Number > 0 {
+		pull = fmt.Sprintf("Pull request %s #%d", repoName(repository), l.Number)
+	}
+	long, limit := "for too long", ""
+	if d, err := time.ParseDuration(l.For); err == nil {
+		long = "for " + humanDuration(d)
+	}
+	if d, err := time.ParseDuration(l.Bound); err == nil {
+		limit = ", past its limit of " + humanDuration(d)
+	}
+	which := "Its merge check"
+	if len(l.Waiting) > 0 {
+		which = "Its merge check (" + strings.Join(l.Waiting, ", ") + ")"
+	}
+	if o.Resolver == conditions.ResolverOperator {
+		needs = "push a new commit to its branch, which asks the check again, or see whether the check still waits " +
+			"in the build seat's queue: mesh-controller.queue."
+	}
+	return fmt.Sprintf("%s has a merge check that has not answered %s", pull, long),
+		fmt.Sprintf("%s is open on a branch that requires the merge check. %s was asked and has not answered %s%s. "+
+			"It cannot merge until its check answers.", pull, which, long, limit),
+		fmt.Sprintf("%s has an answer from its merge check, or is closed", pull), needs, nil
+}
+
 // causeWords is a hand-act's cause as a person says it.
 func causeWords(cause string) string {
 	return strings.NewReplacer(".", " ", "_", " ").Replace(cause)