Complete hidden commands flags and its subcommands

[didrocks]

This change enable to have a correct completion on hidden commands flags and
its subcommands if present, when using bash.
If an exact hidden command is typed on the command line and then the
user request completion, instead of printing other available subcommand
at the same level (which is thus incorrect), it will print any of its
subcommand if available.
Flags completion request (starting with -) will also work as expected,
as well as flag completion request on any subcommand (persistent flags
or local).

Here is an example file, with 2 commands below the root commands (one shown, one hidden), local and persistent flags, and a subcommand of the hidden command:

package main

import (
	"fmt"
	"os"

	"github.com/spf13/cobra"
)

var (
	rootCmd = &cobra.Command{
		Use: "foo",
		Run: func(cmd *cobra.Command, args []string) {},
	}

	displayed = &cobra.Command{
		Use: "displayed",
		Run: func(cmd *cobra.Command, args []string) {},
	}

	hidden = &cobra.Command{
		Use:    "hidden",
		Hidden: true,
		Run:    func(cmd *cobra.Command, args []string) {},
	}

	subHidden = &cobra.Command{
		Use: "subhidden",
		Run: func(cmd *cobra.Command, args []string) {},
	}
)

func init() {
	rootCmd.AddCommand(displayed, hidden)
	rootCmd.PersistentFlags().Bool("global", false, "")
	rootCmd.Flags().Bool("local-flag-on-root", false, "")

	hidden.AddCommand(subHidden)
	hidden.Flags().Bool("flag-on-hidden", false, "")
	subHidden.Flags().Bool("flag-on-subcmd-subhidden", false, "")
}

func main() {
	if err := rootCmd.Execute(); err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
}

Before the patch:

$ foo [tab] # becomes "foo displayed"
# the other command is hidden
$ foo subhid[tab][tab] # -> nothing
# the command is hidden
$ foo hidden [tab] # becomes "foo hidden displayed".
# This is  invalid and likely not executable (2 commands of the same level used). The completion is then incorrect.
$ foo hidden --[tab][tab]
--global              --local-flag-on-root  
# persistent and local flag on root proposed. This is incorrect as the local flag on root isn't available on hidden. Local flag on hidden isn't proposed.
$ foo hidden subhidden --[tab][tab]
--global              --local-flag-on-root  
# Same than above. The local flag isn't avilable on subhidden and its local flag isn't proposed.

After the patch:

$ foo [tab] # becomes "foo displayed"
# the other command is hidden
$ foo subhid[tab][tab] # -> nothing
# the command is hidden
$ foo hidden [tab] # becomes "foo hidden subhidden"
# subcommand of hidden command correct completion
$ foo hidden --[tab][tab]
--flag-on-hidden  --global
# persistent flag on root and local flag on hidden command proposed      
$ foo hidden subhidden --[tab][tab]
--flag-on-subcmd-subhidden  --global 
# persistent flag on root and local flag on subhidden proposed      

As you can see, the impacts are only once you fully typed the hidden command, which will then propose the correct subcommand levels and associated flags, and prevent the invalid proposals.

This fixes the "completion part" of bug #981

[CLAassistant]

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[github-actions]

This PR is being marked as stale due to a long period of inactivity