Pin the json names of manifests, locks and inputs2 by the encoded bytes (issue 1442, review round 1)

Go decodes keys case-insensitively, so a round trip could not see a dropped tag; the encoded bytes now name each field and an older message re-encodes to its own bytes.

go/delivery/forge_inputs_test.go

@@ -21,6 +21,11 @@ func TestForgeMergedCarriesManifestsAndLocks(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	for _, frag := range []string{`"manifests":{"a":`, `"locks":{"a":{"go.sum":`} {
+		if !strings.Contains(string(data), frag) {
+			t.Errorf("the encoding lacks %s: %s", frag, data)
+		}
+	}
 	got, err := DecodeForge(data)
 	if err != nil {
 		t.Fatal(err)
@@ -97,8 +102,9 @@ func TestForgeFromAnOlderBridge(t *testing.T) {
 		t.Fatalf("%+v, %v", f, err)
 	}
 	data, err := EncodeForge(f)
-	if err != nil || strings.Contains(string(data), "manifests") || strings.Contains(string(data), "locks") {
+	// the older message is written with the struct's key order, so the bytes compare as they are
-		t.Errorf("%s, %v", data, err)
+	if err != nil || string(data) != old {
+		t.Errorf("%s, %v, want exactly %s", data, err, old)
 	}
 }
 
@@ -113,6 +119,9 @@ func TestModuleKeepsInputs2(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	if !strings.Contains(string(data), `"inputs2":{"tree":"t1"`) {
+		t.Errorf("the encoding lacks inputs2: %s", data)
+	}
 	got, err := DecodeModule(data)
 	if err != nil {
 		t.Fatal(err)