Cite the controller's lines rightly, and say the newest key holds an id (issue 1223, review round 1)

go/delivery/buildrecord.go

@@ -24,7 +24,7 @@ type BuildRecord struct {
 const BuildsBucket = "mesh-controller_builds"
 
 // BuildKey is a build's record under its module, a build that knew none under the request's key: copied from
-// mesh-controller internal/chain/keys.go:35-41 (BuildKey, with RequestKey at line 43).
+// mesh-controller internal/chain/keys.go:35-40 (BuildKey, with RequestKey at line 42).
 func BuildKey(module, id string) string {
 	if module == "" {
 		return "req." + id
@@ -32,5 +32,7 @@ func BuildKey(module, id string) string {
 	return module + ".build." + id
 }
 
-// NewestKey is the key of a module's newest build, of any state: copied from mesh-controller internal/chain/keys.go:46.
+// NewestKey is the key of a module's newest build, of any state: copied from mesh-controller internal/chain/keys.go:44.
+// The key holds no record: its value is the newest build's id as raw bytes (internal/inventory/chain_builds.go:210 and
+// :546), and the record lives at BuildKey(module, id). The pointer is a hint, checked against that record.
 func NewestKey(module string) string { return module + ".newest" }

go/delivery/buildrecord_test.go

@@ -70,7 +70,7 @@ func TestBuildRecordWithoutInputs(t *testing.T) { // 1223/AC2
 
 func TestBuildKeys(t *testing.T) { // 1223/AC3
 	// Literal values of mesh-controller internal/broker/controller_buckets.go:101 (BucketName(ControllerSeat, ChainBuilds)
-	// is "mesh-controller_builds") and internal/chain/keys.go:35-46.
+	// is "mesh-controller_builds") and internal/chain/keys.go:35-44.
 	if BuildsBucket != "mesh-controller_builds" {
 		t.Errorf("BuildsBucket = %q", BuildsBucket)
 	}