How to associate a category of flags to a category of commands?

[louisroyer]

I have multiple top-level commands (that I don't want to become sub-commands), some of them require a common flag config, while some other must be able to run without this argument.

The naive approach would be to make the flag optional manually check in each command's Action if cmd.String("config") == "", but this is a lot of duplicated code, and the resulting generated help text is not making conditions to include this flag obvious from user point of view.

I also tried the following, but apparently flags categories and commands categories are just cues in the generated help text and have no effect on the flag parsing:

package main

import (
	"context"
	"log"
	"os"

	"github.com/urfave/cli/v3"
)

func main() {
	cmd := &cli.Command{
		Flags: []cli.Flag{
			&cli.StringFlag{
				Name:     "config",
				Required: true,
				Category: "with-config-file",
			},
		},
		Commands: []*cli.Command{
			{
				Name: "noop",
			},
			{
				Name:     "add",
				Category: "with-config-file",
			},
			{
				Name:     "remove",
				Category: "with-config-file",
			},
		},
	}

	if err := cmd.Run(context.Background(), os.Args); err != nil {
		log.Fatal(err)
	}
}

What would be the best way to solve this issue?