Completions do not suggest sub-commands if there are ValidArgs

[marckhouzam]

When a command has both ValidArgs and sub-commands, the completion script only proposes the ValidArgs. Cobra should do also propose non-hidden sub-commands in the completions list.

I cannot see a reason not to do this...

This was brought up in #1035 (comment)

To illustrate, in the program below, the rootCmd specifies ValidArgs of rs and ds, but also has a sub-command pod. The bash completion script will only propose the values of ValidArgs and not the sub-commands when both are present. In this case testprog [tab][tab] will not suggest pod because there are ValidArgs.

Program to reproduce:

package main

import (
	"fmt"
	"os"

	"github.com/spf13/cobra"
)

var rootCmd = &cobra.Command{
	ValidArgs: []string{/*"pod",*/ "rs", "ds"},
	Args:      cobra.ExactArgs(1),
	Use:       "testprog1",
	Run: func(cmd *cobra.Command, args []string) {
		fmt.Println("rootCmd called")
	},
}

var childCmd = &cobra.Command{
	Use: "pod",
	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.BashCompDirective) {
		return []string{"these", "are", "custom", "completions"}, cobra.BashCompDirectiveDefault
	},
	Run: func(cmd *cobra.Command, args []string) {
		fmt.Println("child called")
	},
}

var childCmd2 = &cobra.Command{
	Use: "svc",
	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.BashCompDirective) {
		return []string{"second", "level"}, cobra.BashCompDirectiveDefault
	},
	Run: func(cmd *cobra.Command, args []string) {
		fmt.Println("child called")
	},
}

var completionCmd = &cobra.Command{
	Use: "completion",
	Run: func(cmd *cobra.Command, args []string) {
		cmd.Root().GenBashCompletion(os.Stdout)
	},
}

func main() {
	rootCmd.AddCommand(childCmd)
	rootCmd.AddCommand(completionCmd)
	childCmd.AddCommand(childCmd2)
	rootCmd.Execute()
}