Compare a build with the one the mesh registered, not the newest, which may be one put back (review of #336, hq issue 721)

cmd/mesh-builder/main.go

@@ -329,7 +329,7 @@ func answer(ctx context.Context, publisher builder.Publisher, on, workspace stri
 		// at build time has no reuse key anyway, so nothing is lost by refusing it here.
 		if isRegistry && len(spec.Builds) > 0 {
 			spec.BuildWith = &builder.CheckBuilding{Publish: publisher, Scratch: registryHere, Held: request.Held,
-				Seats: request.Seats, Named: namedOf(request.Check.Named)}
+				Running: request.Check.Running, Seats: request.Seats, Named: namedOf(request.Check.Named)}
 		}
 		var v builder.CheckVerdict
 		v, err = builder.Check(building, builder.Command, spec, workspace, registry, forgeFrom(), say)

cmd/mesh-controller/build.go

@@ -899,6 +899,34 @@ type answers struct {
 //
 // Routed through the artifact store as the network reaches it now (novox/hq 04-ISSUES/102): a
 // base is recorded by digest and path, and a build machine needs something it can pull.
+// runningBy is, keyed "<module>/<artifact>", each artifact of the build the mesh has registered for its module, as a
+// builder reaches the artifact store (novox/hq issue 721): what a check compares its builds with. Empty when it cannot
+// be read, said, and then nothing is said unchanged.
+func runningBy(ctx context.Context) map[string]string {
+	open, err := openStores(ctx)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "could not read what this mesh runs, so the check compares nothing: %v\n", err)
+		// empty-on-error: said above; a check given nothing to compare with says no module unchanged, and all move
+		return nil
+	}
+	defer open.Close()
+	running, err := open.inventory.RegisteredHeld(ctx)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "could not read what this mesh runs, so the check compares nothing: %v\n", err)
+		// empty-on-error: said above; a check given nothing to compare with says no module unchanged, and all move
+		return nil
+	}
+	address, err := whereABuilderReachesTheStore(ctx, open.inventory)
+	if err != nil || address == "" {
+		return running
+	}
+	routed := make(map[string]string, len(running))
+	for key, reference := range running {
+		routed[key] = catalogue.Rerouted(reference, address)
+	}
+	return routed
+}
+
 func heldBy(ctx context.Context) map[string]string {
 	open, err := openStores(ctx)
 	if err != nil {

cmd/mesh-controller/checks.go

@@ -269,7 +269,7 @@ func checkRequestFor(ctx context.Context, open *stores, p link.PullUpdated, scop
 		Check: &link.CheckRequest{Owner: p.Owner, Repo: p.Repo, Number: p.Number, Base: p.Base,
 			Paths: p.Paths, Beside: beside, Modules: scope.Modules, Dependents: scope.Dependents, New: scope.New,
 			Manifests: scope.Manifests, Judge: scope.Judge, Builds: builds, Named: namedForTheCheck(ctx, p, builds),
-			Release: release},
+			Release: release, Running: runningBy(ctx)},
 	}, nil
 }
 

cmd/mesh-controller/same_program.go

@@ -107,7 +107,7 @@ func leaveSameAsRunning(ctx context.Context, inv *inventory.Inventory, plan *inv
 		// empty-on-error: said above; nothing left out of the walk is the safe answer, every module moves as before
 		return nil
 	}
-	held, err := inv.Held(ctx)
+	held, err := inv.RegisteredHeld(ctx)
 	if err != nil {
 		fmt.Printf("  what the mesh holds could not be read, so every module moves: %v\n", err)
 		// empty-on-error: said above; nothing left out of the walk is the safe answer, every module moves as before