add options command for show global flag

Signed-off-by: Alan Zhu <zg.zhu@daocloud.io>

cmd/helm/options.go

@@ -0,0 +1,47 @@
+/*
+Copyright The Helm Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"github.com/spf13/cobra"
+	"helm.sh/helm/v3/cmd/helm/require"
+	"io"
+	"k8s.io/kubectl/pkg/util/templates"
+)
+
+// NewCmdOptions implements the options command
+func newCmdOptions(out io.Writer) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "options",
+		Short: "print the list of flags inherited by all commands",
+		Long:  "print the list of flags inherited by all commands",
+		Args:  require.NoArgs,
+		Run: func(cmd *cobra.Command, args []string) {
+			cmd.Usage()
+		},
+	}
+
+	// The `options` command needs to write its output to the `out` stream
+	// (typically stdout). Without calling SetOutput here, the Usage()
+	// function call will fall back to stderr.
+	//
+	// See https://github.com/kubernetes/kubernetes/pull/46394 for details.
+	cmd.SetOutput(out)
+
+	templates.UseOptionsTemplates(cmd)
+	return cmd
+}

cmd/helm/root.go

@@ -71,9 +71,12 @@ By default, the default directories depend on the Operating System. The defaults
 
 func newRootCmd(actionConfig *action.Configuration, out io.Writer, args []string) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:                    "helm",
-		Short:                  "The Helm package manager for Kubernetes.",
-		Long:                   globalUsage,
+		Use:   "helm",
+		Short: "The Helm package manager for Kubernetes.",
+		Long:  globalUsage,
+		Run: func(cmd *cobra.Command, args []string) {
+			cmd.Help()
+		},
 		SilenceUsage:           true,
 		BashCompletionFunction: completion.GetBashCustomFunction(),
 	}
@@ -178,6 +181,7 @@ func newRootCmd(actionConfig *action.Configuration, out io.Writer, args []string
 		newEnvCmd(out),
 		newPluginCmd(out),
 		newVersionCmd(out),
+		newCmdOptions(out),
 
 		// Hidden documentation generator command: 'helm docs'
 		newDocsCmd(out),