Show and change the build queue through the controller, and have plans follow it (hq ADR 0219)

Nothing showed what waited for a build machine, and an ask could not be
dropped without leaving the plan that made it waiting for ever. New verbs:
queue, cancel, clear, rebuild, replay, kill, pause, resume, and plans retry.
Every ask a person drops is recorded failed through the same take-in as a
failed build; a plan keeps the id it asked each module under and matches
its outcome by it. replay is a dry run unless registered, and registering
an older commit than one registered since needs --older (hq issue 207).
A plan waiting on a seat paused on every holder says so and is not late;
a failed plan can be retried, and a rebuild joins the plan holding the
module instead of running beside it.

cmd/mesh-controller/main.go

@@ -73,6 +73,21 @@ func run() error {
 		return askCommand(ctx, args[1:])
 	case "builds":
 		return buildsCommand(ctx, args[1:])
+	// The build queue, controlled by hand (novox/hq ADR 0219).
+	case "queue":
+		return queueCommand(ctx, args[1:])
+	case "cancel":
+		return cancelCommand(ctx, args[1:])
+	case "clear":
+		return clearCommand(ctx, args[1:])
+	case "rebuild":
+		return rebuildCommand(ctx, args[1:])
+	case "replay":
+		return replayCommand(ctx, args[1:])
+	case "kill":
+		return killCommand(ctx, args[1:])
+	case "pause", "resume":
+		return pauseCommand(ctx, args[0], args[1:])
 	case "collection":
 		return collectionCommand(ctx, args[1:])
 	case "plans":
@@ -202,6 +217,14 @@ func usage() {
   build --behind                 build every module the mesh holds older than its source
   build --on <module>            rebuild every module that stands on this module's artifacts, bases first
   builds [<module>]              what has been built lately, and what came of it
+  queue [--json]                 every ask in the build queue: waiting, in flight (where, how long), dead
+  cancel <id>                    drop a waiting or dead ask; recorded failed, cancelled by hand
+  clear [--dead]                 cancel every waiting ask (and the dead ones); never one in flight
+  rebuild <module|build-id>      ask the module's source again, or that build's, under a new id
+  replay <build-id> [--register [--older]]   that build's commit again; a dry run unless --register
+  kill <id>                      end a build where it runs; recorded failed, killed by hand
+  pause [<node>] / resume [<node>]   the build seat's holder there, or every holder, takes nothing new / again
+  plans retry <id>               ask a failed plan's failed builds again, and carry the plan on
   collection [--json]            kept archives held/unheld by a manifest, and what the sweep may let go
   builder issue <name>           a broker account for a build machine, scoped to build work,
                                  delivered as the builder module's broker secret (module add it first)
@@ -271,7 +294,7 @@ func (b builds) Built(ctx context.Context, result link.BuildResult) error {
 	case err != nil && result.Failed != "":
 		fmt.Printf("%s: %v\n", result.ID, err)
 		if result.Module != "" {
-			planBuilt(ctx, b.open, result.Module, result.Commit, result.Failed, asked)
+			planBuilt(ctx, b.open, result.Module, result.Commit, result.Failed, asked, result.ID)
 		} else {
 			planFailedBuild(ctx, b.open, result)
 		}
@@ -280,18 +303,18 @@ func (b builds) Built(ctx context.Context, result link.BuildResult) error {
 		// Not a failure: the module is already at what a later request built. A plan that asked
 		// before that later request is answered by it; one that asked after it ignores this.
 		fmt.Printf("%s: %v\n", result.ID, err)
-		planBuilt(ctx, b.open, manifest.Module, result.Commit, "", asked)
+		planBuilt(ctx, b.open, manifest.Module, result.Commit, "", asked, result.ID)
 		return nil
 	case err != nil:
 		fmt.Printf("%s: heard and recorded, and not registered: %v\n", result.ID, err)
 		if manifest.Module != "" {
-			planBuilt(ctx, b.open, manifest.Module, result.Commit, err.Error(), asked)
+			planBuilt(ctx, b.open, manifest.Module, result.Commit, err.Error(), asked, result.ID)
 		}
 		return nil
 	}
 	fmt.Printf("%s: %s %s registered, built on %s from %s\n",
 		result.ID, manifest.Module, manifest.Version, result.On, short(result.Commit))
 	saysWhenThePolicyActs(ctx, b.inv, manifest.Module)
-	planBuilt(ctx, b.open, manifest.Module, result.Commit, "", asked)
+	planBuilt(ctx, b.open, manifest.Module, result.Commit, "", asked, result.ID)
 	return nil
 }