Rebased and addressed PR comments

cmd/completion.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2020 The Kubernetes 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 (
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+func newCompletionCmd() *cobra.Command {
+	completionCmd := &cobra.Command{
+		Use:   "completion",
+		Short: "Generators for shell completions",
+	}
+	completionCmd.AddCommand(newZshCmd())
+	completionCmd.AddCommand(newBashCmd())
+	return completionCmd
+}
+
+func newBashCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "bash",
+		Short: "Generate bash completions",
+		RunE: func(cmd *cobra.Command, cmdArgs []string) error {
+			return cmd.Root().GenBashCompletion(os.Stdout)
+		},
+	}
+}
+
+func newZshCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "zsh",
+		Short: "Generate zsh completions",
+		RunE: func(cmd *cobra.Command, cmdArgs []string) error {
+			return cmd.Root().GenZshCompletion(os.Stdout)
+		},
+	}
+}

cmd/main.go

@@ -123,6 +123,9 @@ func buildCmdTree() *cobra.Command {
 	// kubebuilder version
 	rootCmd.AddCommand(version.NewVersionCmd())
 
+	// kubebuilder completion
+	rootCmd.AddCommand(newCompletionCmd())
+
 	return rootCmd
 }