Say why assign finds no module, and keep an assignment pending on its build

A merge asks for a new module's build, and assign answered "no module of that
name" until the build registered it, which read as a module nobody registered
(hq issue 325). Keep every build request, tell a build in flight, a module
known and not built, and an unknown name apart, and make an assignment made
while the build runs when the build registers the module.

cmd/mesh-controller/status.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"os"
 	"sort"
 	"strings"
 	"time"
@@ -143,6 +144,8 @@ func printStatus(asked answers) error {
 			len(quiet), strings.Join(said, "\n  "))
 	}
 
+	printPending(asked.pending, asked.pendingUnread)
+
 	if open, late := openPlans(asked.plans, time.Now(), asked.paused, asked.tierBounds); len(open) > 0 {
 		fmt.Printf("%d plan(s) open", len(open))
 		if late > 0 {
@@ -466,6 +469,15 @@ func theThreeQuestions(ctx context.Context, open *stores) (answers, error) {
 	if out.conditions, err = openConditions(ctx); err != nil {
 		out.conditionsUnread = err.Error()
 	}
+	// And the assignments waiting for their module's build (novox/hq issue 325): what a missed outcome left
+	// waiting is settled first, so one never waits silently past its build.
+	for _, line := range settleStalePending(ctx, open, time.Now()) {
+		fmt.Fprintln(os.Stderr, line)
+	}
+	if out.pending, err = inv.Pending(ctx, time.Now().Add(-pendingShownFor)); err != nil {
+		out.pendingUnread = err.Error()
+		err = nil
+	}
 	out.plans, err = inv.RecentPlans(ctx, 5)
 	if err != nil {
 		return answers{}, err
@@ -598,7 +610,53 @@ func (a answers) well() bool {
 	return len(a.wrong) == 0 && len(a.quiet) == 0 && len(a.behind) == 0 &&
 		len(a.waiting) == 0 && len(a.refused) == 0 && a.network == "" && len(a.untaken) == 0 &&
 		len(a.filtered) == 0 && len(a.unheld) == 0 && len(a.overflowing) == 0 &&
-		len(a.conditions) == 0 && a.conditionsUnread == ""
+		len(a.conditions) == 0 && a.conditionsUnread == "" && a.pendingUnread == "" && !pendingNotWell(a.pending)
+}
+
+// pendingNotWell is whether any pending assignment is waiting, or ended without being made.
+func pendingNotWell(pending []inventory.PendingAssignment) bool {
+	for _, p := range pending {
+		if p.State != inventory.PendingApplied && p.State != inventory.PendingWithdrawn {
+			return true
+		}
+	}
+	return false
+}
+
+// printPending says the assignments waiting for their module's build, and those ended in the last day
+// (novox/hq issue 325).
+func printPending(pending []inventory.PendingAssignment, unread string) {
+	if unread != "" {
+		fmt.Printf("the assignments waiting for a build could not be read: %s\n\n", unread)
+		return
+	}
+	var waiting, ended []inventory.PendingAssignment
+	for _, p := range pending {
+		if p.State == inventory.PendingWaiting {
+			waiting = append(waiting, p)
+		} else {
+			ended = append(ended, p)
+		}
+	}
+	if len(waiting) > 0 {
+		fmt.Printf("%d assignment(s) wait for their module's build to register it:\n", len(waiting))
+		for _, p := range waiting {
+			fmt.Printf("  %-12s %-20s build %s of %s %s, since %s\n", p.Node, p.Module, p.Build, p.Repository,
+				orRoot(p.Path), clock(p.Since))
+		}
+		fmt.Printf("\n  each is made when its build registers the module; `unassign <node> <module>` withdraws it\n\n")
+	}
+	if len(ended) > 0 {
+		fmt.Printf("%d pending assignment(s) ended in the last day:\n", len(ended))
+		for _, p := range ended {
+			at := ""
+			if p.Settled != nil {
+				at = clock(*p.Settled)
+			}
+			fmt.Printf("  %-12s %-20s %-9s %s\n  %-12s %s\n", p.Node, p.Module, p.State, at, "", p.Note)
+		}
+		fmt.Println()
+	}
 }
 
 // hostSplit is which machines report which host version, for every version more than one machine