Add invocation-owned Cobra sessions

internal/cobra/performance_test.go

@@ -38,6 +38,30 @@ func BenchmarkPerformanceParse(b *testing.B) {
 	}
 }
 
+func BenchmarkPerformanceSessionParseAndHelp(b *testing.B) {
+	root := performanceFlatTree(8)
+	args := []string{"wide007"}
+	session := Prepare(root, ParseOptions{Context: context.Background(), Out: io.Discard, Err: io.Discard})
+	result := session.Parse(args)
+	if result.Failure != nil {
+		b.Fatalf("fixture parse failed: %s", result.Failure.Message)
+	}
+	if help, failure := session.RenderHelp(result.Path); failure != nil || help == "" {
+		b.Fatalf("fixture help failed: %q %v", help, failure)
+	}
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		result := session.Parse(args)
+		if result.Failure != nil {
+			b.Fatalf("parse failed: %s", result.Failure.Message)
+		}
+		if help, failure := session.RenderHelp(result.Path); failure != nil || help == "" {
+			b.Fatalf("help failed: %q %v", help, failure)
+		}
+	}
+}
+
 func performanceFlatTree(count int) *Command {
 	root := &Command{Name: "app", Children: make([]*Command, count)}
 	for index := range root.Children {