Allow to customize shell completion

[suzuki-shunsuke]

https://cli.urfave.org/v3/examples/completions/shell-completions/

What

EnableShellCompletion: true is useful, but I'd like to customize the command's description, usage, and Hidden.
I don't want to hide completion command because users run this command.

cli/completion.go

Line 45 in c88e6fc

Hidden: true,

Current problem

Command.Run adds a sub command completion if EnableShellCompletion is true, but there is no way to customize the command.

cli/command_run.go

Lines 93 to 95 in 103c934

	func (cmd *Command) Run(ctx context.Context, osArgs []string) (deferErr error) {
	tracef("running with arguments %[1]q (cmd=%[2]q)", osArgs, cmd.Name)
	cmd.setupDefaults(osArgs)

cli/command_setup.go

Lines 91 to 105 in 103c934

	if cmd.EnableShellCompletion || cmd.Root().shellCompletion {
	completionCommand := buildCompletionCommand(cmd.Name)
	if cmd.ShellCompletionCommandName != "" {
	tracef(
	"setting completion command name (%[1]q) from "+
	"cmd.ShellCompletionCommandName (cmd=%[2]q)",
	cmd.ShellCompletionCommandName, cmd.Name,
	)
	completionCommand.Name = cmd.ShellCompletionCommandName
	}
	tracef("appending completionCommand (cmd=%[1]q)", cmd.Name)
	cmd.appendCommand(completionCommand)
	}

If you add a command completion explicitly, EnableShellCompletion does nothing because cmd.appendCommand(completionCommand) skips adding a command and doesn't change the custom completion command.

cli/command.go

Lines 299 to 304 in c88e6fc

	func (cmd *Command) appendCommand(aCmd *Command) {
	if !slices.Contains(cmd.Commands, aCmd) {
	aCmd.parent = cmd
	cmd.Commands = append(cmd.Commands, aCmd)
	}
	}

If buildCompletionCommand is public, you can create a completion command and customize it and append it to Commands,
but actually buildCompletionCommand is private.

https://cli.urfave.org/v3/examples/completions/shell-completions/ refers how to customize the completion command, but it doesn't work fine it doesn't customize completion command fields such as Hidden.

How to solve

I propose two options.

1. Add fields to cli.Command to customize completion commands
2. Publish buildCompletionCommand

I disagree the option 1.
By option 2, you can cusomize the completion command.

	cmd := &cli.Command{} // Define a Root command
	completion := cli.BuildCompletionCommand(cmd.Name) // Create a completion command by buildCompletionCommand
	completion.Hidden = false // Customize completion command
	cmd.Commands = append(cmd.Commands, completion) // Append completion command

[suzuki-shunsuke]

I created a pull request.

• Enable to customize completion commands #2103