sort-cli: add benchmark

sort-cli/main_test.go

@@ -55,3 +55,12 @@ func TestFlags(t *testing.T) {
 		})
 	}
 }
+
+func BenchmarkRun(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		flag.CommandLine = flag.NewFlagSet("Bench", flag.ExitOnError)
+		os.Args = append([]string{"Bench"}, "testdata/first")
+
+		_ = run()
+	}
+}