Keep a walk's withheld modules on its record, name every machine a stopped send reached, and list the stop's store tests (review of #232)

cmd/mesh-controller/issue459_test.go

@@ -391,3 +391,22 @@ func TestSavingPlansAndMovingMergesIsOneAct(t *testing.T) {
 		t.Fatalf("the merge moved to %q though the act was refused", m.Plan)
 	}
 }
+
+// What a stopped walk leaves on the machines names every machine its sends reached (review of #232): a module sent
+// with no first machine reached every machine running it; one sent first reached those, and the rest it was sent
+// to; a module a merge walked again moves is sent again, and is not named.
+func TestKeptNamesEveryMachineASendReached(t *testing.T) {
+	at := t0
+	p := inventory.Plan{Modules: map[string]*inventory.PlanModule{
+		"together": {SentAt: &at},
+		"first":    {First: []string{"anchor"}, FirstAt: &at, Rest: map[string]inventory.SentDeclaration{"laptop": {}}},
+		"again":    {SentAt: &at},
+		"unsent":   {},
+	}}
+	got := keptOf(p, []string{"again"}, map[string][]string{"together": {"laptop", "anchor"}, "again": {"anchor"}})
+	want := []inventory.PlanKept{{Module: "first", Machines: []string{"anchor", "laptop"}},
+		{Module: "together", Machines: []string{"anchor", "laptop"}}}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("kept %+v; want %+v", got, want)
+	}
+}