WIP - e2e: distinct help messages with and without extended options

Flags defined via the framework/config package are considered less
important and only shown when explicitly requested via --full-help.

WIP! This commit merely shows how this could be done. For it to be
useful, all non-essential flags would have to be defined via
framework/config.

While at it, this commit also fixes a small usability issue:
previously the e2e.test silently ignored additional parameters.

test/e2e/framework/BUILD

@@ -126,6 +126,7 @@ go_library(
         "//staging/src/k8s.io/client-go/util/retry:go_default_library",
         "//staging/src/k8s.io/csi-api/pkg/client/clientset/versioned:go_default_library",
         "//staging/src/k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset:go_default_library",
+        "//test/e2e/framework/config:go_default_library",
         "//test/e2e/framework/ginkgowrapper:go_default_library",
         "//test/e2e/framework/metrics:go_default_library",
         "//test/e2e/manifest:go_default_library",

test/e2e/framework/config/config.go

@@ -80,10 +80,11 @@ import (
 	"unicode/utf8"
 )
 
-// CommandLine is the flag set that AddOptions adds to. Usually this
-// is the same as the default in the flag package, but can also be
-// something else (for example during testing).
-var CommandLine = flag.CommandLine
+// CommandLine is the flag set that AddOptions adds to. This
+// is distinct from the global default in the flag package, so
+// these additional flags can be treated separately from other
+// flags if desired.
+var CommandLine = flag.NewFlagSet("config", flag.ContinueOnError)
 
 // AddOptions analyzes the options value and creates the necessary
 // flags to populate it.

test/e2e/framework/test_context.go

@@ -30,6 +30,7 @@ import (
 	"k8s.io/client-go/tools/clientcmd"
 	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
 	kubeletconfig "k8s.io/kubernetes/pkg/kubelet/apis/config"
+	e2econfig "k8s.io/kubernetes/test/e2e/framework/config"
 )
 
 const defaultHost = "http://127.0.0.1:8080"
@@ -295,11 +296,49 @@ func RegisterNodeFlags() {
 	flag.StringVar(&TestContext.SystemSpecName, "system-spec-name", "", "The name of the system spec (e.g., gke) that's used in the node e2e test. The system specs are in test/e2e_node/system/specs/. This is used by the test framework to determine which tests to run for validating the system requirements.")
 }
 
+func CopyFlags(from, to *flag.FlagSet) {
+	from.VisitAll(func(f *flag.Flag) {
+		to.Var(f.Value, f.Name, f.Usage)
+	})
+}
+
 // HandleFlags sets up all flags and parses the command line.
 func HandleFlags() {
 	RegisterCommonFlags()
 	RegisterClusterFlags()
-	flag.Parse()
+
+	help := flag.Bool("help", false, "show common flags")
+	fullHelp := flag.Bool("full-help", false, "show all flags, including the less commonly used ones")
+	// We copy all flags (normal and config) into a single flag
+	// set and then parse in one go. The default usage
+	// instructions only dump the normal flags. If users want to see
+	// all available options, they can use --full-help or dump
+	// a sample config file.
+	allFlags := flag.NewFlagSet(os.Args[0], flag.ContinueOnError)
+	CopyFlags(flag.CommandLine, allFlags)
+	CopyFlags(e2econfig.CommandLine, allFlags)
+	err := allFlags.Parse(os.Args[1:])
+	if err == flag.ErrHelp || *help {
+		fmt.Fprintf(flag.CommandLine.Output(), "Common flags for %s:\n", os.Args[0])
+		flag.CommandLine.PrintDefaults()
+		os.Exit(1)
+	}
+	if err != nil {
+		os.Exit(1)
+	}
+	if *fullHelp {
+		fmt.Fprintf(flag.CommandLine.Output(), "All flags for %s:\n", os.Args[0])
+		flag.CommandLine.PrintDefaults()
+		os.Exit(1)
+	}
+	if allFlags.NArg() > 0 {
+		// We have no support for additional parameters. We
+		// intentionally do not dump valid parameters here
+		// because the list would be too long, making it
+		// harder to spot the error message.
+		fmt.Fprintf(os.Stderr, "Unrecognized parameters for %s, see --full-help: %v\n", os.Args[0], allFlags.Args())
+		os.Exit(1)
+	}
 }
 
 func createKubeConfig(clientCfg *restclient.Config) *clientcmdapi.Config {