Preflight comparison transaction names

internal/comparison/publish_test.go

@@ -506,6 +506,49 @@ func TestPublishReplacesEmptyDirectory(t *testing.T) {
 	}
 }
 
+func TestComparisonDestinationPreflightsTransactionSiblingNames(t *testing.T) {
+	workingDirectory := t.TempDir()
+	missingParent := filepath.Join(workingDirectory, "missing")
+	target := filepath.Join(missingParent, strings.Repeat("a", maxComparisonComponentBytes+1))
+	if _, err := PlanDestination(workingDirectory, target, false); err == nil {
+		t.Fatal("PlanDestination() accepted an overlong destination name")
+	}
+	if _, err := os.Lstat(missingParent); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("missing parent stat error = %v, want not exist", err)
+	}
+}
+
+func TestPublishSupportsLongestDestinationComponent(t *testing.T) {
+	workingDirectory := t.TempDir()
+	parent := filepath.Join(workingDirectory, "nested")
+	target := filepath.Join(parent, strings.Repeat("a", maxComparisonComponentBytes))
+
+	plan, err := PlanDestination(workingDirectory, target, false)
+	if err != nil {
+		t.Fatalf("PlanDestination() error = %v", err)
+	}
+	if _, err := Publish(context.Background(), plan, testBundle()); err != nil {
+		t.Fatalf("Publish() error = %v", err)
+	}
+	if _, err := RecognizeBundle(target); err != nil {
+		t.Fatalf("RecognizeBundle() error = %v", err)
+	}
+
+	next := testBundle()
+	next.Reports[0].Markdown = []byte("# Replacement\n")
+	plan, err = PlanDestination(workingDirectory, target, true)
+	if err != nil {
+		t.Fatalf("PlanDestination(replace) error = %v", err)
+	}
+	if _, err := Publish(context.Background(), plan, next); err != nil {
+		t.Fatalf("Publish(replace) error = %v", err)
+	}
+	if data := readFile(t, filepath.Join(target, "01-weather-light.md")); string(data) != "# Replacement\n" {
+		t.Fatalf("replacement report = %q", data)
+	}
+	assertOnlyDestinationEntry(t, parent, filepath.Base(target))
+}
+
 func TestPublishReportsCommittedBundleWhenBackupCleanupFails(t *testing.T) {
 	workingDirectory := t.TempDir()
 	target := filepath.Join(workingDirectory, "comparison-daily")