Ask mesh-delivery whether a merge's group still assembles (hq issue 525)

A merge from any head waited for the window because the controller could not
see a group's members, so the window skip changed nothing in production and
unrelated merges walked one after another. The controller now asks
mesh-delivery's groups, within 3 s and before the plans are held: a merge
waits only when its head's group has another member whose pull request is
open and whose merge it does not keep yet (ADR 0306 §2). No answer means it
waits, and its batch says why. A headed merge in no waiting group and related
to no batch is cut at once, as one from no head is (ADR 0304 §1, ADR 0306 §3).

The controller's grant names mesh-delivery.groups. The installer's first user
list in mesh-host must carry it too before the genesis test can pass.

cmd/mesh-controller/batches_test.go

@@ -34,6 +34,7 @@ func windowed(t *testing.T) *stores {
 		t.Fatal(err)
 	}
 	t.Setenv(mergeWindowFileVar, settings)
+	noGroups(t)
 	if err := inv.RegisterModule(ctx, catalogue.Manifest{Module: "mesh-controller", Version: "1"},
 		inventory.Source{Repository: "novox/mesh-controller", Seat: "git", Ref: "main", BuiltFrom: "c0",
 			Head: "c0"}); err != nil {
@@ -59,9 +60,9 @@ func windowed(t *testing.T) *stores {
 var t0 = time.Now().UTC().Truncate(time.Second)
 
 // catalogueMerge is a merge of the catalogue changing one module's directory, made at a moment, from a pull
-// request's head branch of its own, as the forge announces every merge. A merge from a head may have a group
-// member still to merge, which the controller cannot tell, so it waits for the window (novox/hq ADR 0306
-// decision 2, stillAssembles): these merges keep the window's rules of ADR 0276. lone is one from no head.
+// request's head branch of its own, as the forge announces every merge. Whether its head names a delivery group
+// with a member still to merge is mesh-delivery's word, which windowed stubs as no group at all (noGroups); a test
+// whose merges wait for the window as a group's says so (groupsWaiting).
 func catalogueMerge(commit, module string, made time.Time) link.SourceMoved {
 	return link.SourceMoved{Owner: "novox", Repo: "mesh-catalog", Base: "main", Head: "pr/" + commit, Commit: commit,
 		MergedAt: made.Format(time.RFC3339Nano), Paths: []string{"modules/" + module + "/module.json"},
@@ -74,6 +75,40 @@ func repoMerge(repo, commit string, made time.Time) link.SourceMoved {
 		MergedAt: made.Format(time.RFC3339Nano), Paths: []string{"main.go"}}
 }
 
+// noGroups stubs mesh-delivery's word on groups for a test: no head names a group.
+func noGroups(t *testing.T) {
+	t.Helper()
+	was := deliveryGroupOf
+	deliveryGroupOf = func(context.Context, bool, string) ([]groupMember, bool, error) { return nil, false, nil }
+	t.Cleanup(func() { deliveryGroupOf = was })
+}
+
+// groupsWaiting stubs mesh-delivery's word on groups for a test: each head named is a group with a member of another
+// repository whose pull request is open (novox/elsewhere, ready), so a merge from it waits for the window (ADR 0306
+// decision 2); every other head names no group.
+func groupsWaiting(t *testing.T, heads ...string) {
+	t.Helper()
+	was := deliveryGroupOf
+	deliveryGroupOf = func(_ context.Context, _ bool, head string) ([]groupMember, bool, error) {
+		if slices.Contains(heads, head) {
+			return []groupMember{{Repository: "novox/elsewhere", State: "ready"}}, true, nil
+		}
+		return nil, false, nil
+	}
+	t.Cleanup(func() { deliveryGroupOf = was })
+}
+
+// everyHeadWaits stubs mesh-delivery's word on groups for a test whose merges each wait for the window as they did
+// before novox/hq ADR 0304: every head is a group with a member of another repository still to merge.
+func everyHeadWaits(t *testing.T) {
+	t.Helper()
+	was := deliveryGroupOf
+	deliveryGroupOf = func(context.Context, bool, string) ([]groupMember, bool, error) {
+		return []groupMember{{Repository: "novox/elsewhere", State: "ready"}}, true, nil
+	}
+	t.Cleanup(func() { deliveryGroupOf = was })
+}
+
 // fromHead is a merge from a head branch a test names: merges from one head are members of one delivery group,
 // related by it (novox/hq ADR 0304 decision 1), so they share a batch whatever else they share.
 func fromHead(m link.SourceMoved, head string) link.SourceMoved {
@@ -125,6 +160,7 @@ func walks(t *testing.T, open *stores) (walks, batches []inventory.Plan) {
 // later commit, which names both merges — the earlier carried by the later.
 func TestTwoMergesSecondsApartAreOneWalkAtTheLaterCommit(t *testing.T) {
 	open := windowed(t)
+	everyHeadWaits(t)
 	asked := asksWithPaths(t)
 	claude := catalogueMerge("553b7191claude", "app", t0)
 	dunst := catalogueMerge("48bda475dunst", "notes", t0.Add(17*time.Second))
@@ -169,6 +205,7 @@ func TestTwoMergesSecondsApartAreOneWalkAtTheLaterCommit(t *testing.T) {
 // Merges of three repositories in one window are one walk, one commit for each.
 func TestThreeRepositoriesInOneWindowAreOneWalk(t *testing.T) {
 	open := windowed(t)
+	groupsWaiting(t, "feat/three")
 	asksRecorded(t)
 	for i, r := range []string{"one", "two", "three"} {
 		hear(t, open, fromHead(repoMerge(r, "c-"+r, t0.Add(time.Duration(i)*20*time.Second)), "feat/three"),
@@ -204,6 +241,7 @@ func TestThreeRepositoriesInOneWindowAreOneWalk(t *testing.T) {
 // closes at most ten minutes after its first merge however busy.
 func TestAMergeRestartsTheWindowAndTheMaximumClosesIt(t *testing.T) {
 	open := windowed(t)
+	groupsWaiting(t, "feat/both", "feat/busy")
 	asksWithPaths(t)
 	hear(t, open, fromHead(repoMerge("one", "c1", t0), "feat/both"), t0)
 	hear(t, open, fromHead(repoMerge("two", "c2", t0.Add(80*time.Second)), "feat/both"), t0.Add(80*time.Second))
@@ -217,6 +255,7 @@ func TestAMergeRestartsTheWindowAndTheMaximumClosesIt(t *testing.T) {
 	}
 
 	busy := windowed(t)
+	groupsWaiting(t, "feat/both", "feat/busy")
 	asksWithPaths(t)
 	var last time.Time
 	for i := 0; i < 12; i++ {
@@ -240,6 +279,7 @@ func TestAMergeRestartsTheWindowAndTheMaximumClosesIt(t *testing.T) {
 // what is grouped, and that the plan is not yet calculated. It says so on the bus as plan-moved, too.
 func TestTheAssemblingBatchIsShown(t *testing.T) {
 	open := windowed(t)
+	groupsWaiting(t, "pr/553b7191claude")
 	asksWithPaths(t)
 	var said []inventory.Plan
 	was := inventory.PlanSaved
@@ -377,6 +417,7 @@ func TestAWaitingWalkIsFoldedIntoTheNextBatch(t *testing.T) {
 // moves — named at once on a walk done — and joins the next batch when it does not.
 func TestALateMergeIsAnsweredByTheWalkOfTheLaterOne(t *testing.T) {
 	open := windowed(t)
+	everyHeadWaits(t)
 	asksWithPaths(t)
 	ctx := t.Context()
 	later := catalogueMerge("48bda475dunst", "notes", t0.Add(17*time.Second))
@@ -408,6 +449,7 @@ func TestALateMergeIsAnsweredByTheWalkOfTheLaterOne(t *testing.T) {
 // first; the first delivered answers the older ones, and the search stops.
 func TestAFailedWalkWalksItsEarlierMergesAlone(t *testing.T) {
 	open := windowed(t)
+	everyHeadWaits(t)
 	asked := asksWithPaths(t)
 	ctx := t.Context()
 	// Made before the cut marks their modules seen, as merges are: walked again, they are news all the same.
@@ -476,6 +518,7 @@ func TestAFailedWalkWalksItsEarlierMergesAlone(t *testing.T) {
 func TestAGroupsOrderBecomesTiersInsideTheWalk(t *testing.T) {
 	for _, grouped := range []bool{true, false} {
 		open := windowed(t)
+		everyHeadWaits(t)
 		asksWithPaths(t)
 		ctx := t.Context()
 		for _, m := range []string{"mesh-host"} {
@@ -513,6 +556,7 @@ func TestAGroupsOrderBecomesTiersInsideTheWalk(t *testing.T) {
 // store, a merge handed over again is not doubled, and the batch is cut when its window closes.
 func TestABatchSurvivesARestart(t *testing.T) {
 	open := windowed(t)
+	groupsWaiting(t, "feat/both")
 	asksWithPaths(t)
 	hear(t, open, fromHead(repoMerge("one", "c1", t0), "feat/both"), t0)
 	hear(t, open, fromHead(repoMerge("two", "c2", t0.Add(30*time.Second)), "feat/both"), t0.Add(30*time.Second))
@@ -580,6 +624,7 @@ func TestAWaitingWalkNamesTheMergesItAnswers(t *testing.T) {
 // nothing, and the merge joins the next batch.
 func TestALateMergeOfAOneModuleRepositoryIsNamed(t *testing.T) {
 	open := windowed(t)
+	everyHeadWaits(t)
 	asksWithPaths(t)
 	ctx := t.Context()
 	c2 := repoMerge("one", "c2", t0.Add(-50*time.Second))
@@ -733,6 +778,7 @@ func TestTheCatchUpKeepsWhatACutMadeHistory(t *testing.T) {
 // still waits for the word, so no catalogue delivery skips its turn.
 func TestAMergeOnTheControllersPathNeverSharesABatch(t *testing.T) {
 	open := windowed(t)
+	everyHeadWaits(t)
 	asked := asksWithPaths(t)
 	ctx := t.Context()
 	if err := open.inventory.RegisterModule(ctx, catalogue.Manifest{Module: "mesh-delivery", Version: "1",
@@ -877,6 +923,7 @@ func sameMerge(a, b inventory.PlanMerge) bool {
 // its delivery would skip its turn. It joins the next catalogue batch.
 func TestALateCatalogueMergeIsNotAnsweredByAnOwnPathWalk(t *testing.T) {
 	open := windowed(t)
+	everyHeadWaits(t)
 	asksWithPaths(t)
 	ctx := t.Context()
 	for _, m := range []struct {