Replace Flags library alecthomas/kingpin with spf13/pflag

[ivankatliarchuk]

What would you like to be added:

✅ TL;DR

Use cobra for building modern, extensible CLI applications — especially if you want long-term support, Kubernetes-style UX, and active community backing.

Library spf13/cobra is in pretty much every kubernetes project https://github.com/search?q=org%3Akubernetes-sigs%20github.com%2Fspf13%2Fcobra&type=code

Avoid kingpin for projects. Although it offers a great developer experience, it is archived and no longer maintained.

Library kingpin only used in external-dns

Why is this needed:

⚔️ Comparing cobra vs kingpin for Go CLI Applications

---

📦 Feature Comparison

Feature	cobra	kingpin
Project Status	✅ Actively maintained and widely used	⚠️ Archived (read-only)
Subcommand support	✅ First-class support with nested commands	✅ Strong, elegant support
Help / Usage formatting	✅ Customizable help output	✅ Very clean help output
Flag parsing	✅ Uses pflag for compatibility	✅ Built-in (custom parsing)
Standard flag support	✅ Compatible via pflag	❌ Not compatible
Kubernetes adoption	✅ Used by kubectl, controller-runtime, etc.	❌ Not used
Command structure	✅ Explicit tree structure	✅ Declarative-style chain calls
Validation	✅ Built-in validation	🚫 Not supported out of the box (but possible)
Learning curve	🟡 Slightly verbose at first	🟢 Easy & readable
Last Update	✅ 2+ month ago	❌ 2+ years ago
Github Stars	✅ 40k+	🟡 ~4k

[ivankatliarchuk]

/kind deprecation

[mloiseleur]

It makes sense to me. It's also used with TraefikLabs project ;).

[anshuman-agarwala]

Hi, if this is not taken yet then I would like to work on this.

[mloiseleur]

@anshuman-agarwala Sure. PRs are welcome. /assign @anshuman-agarwala

[ivankatliarchuk]

HI @anshuman-agarwala are you planning to take a stab on that issue anytime soon?

[anshuman-agarwala]

Hi, really sorry for being a no show, I don't think I'll be able to get around to this anytime soon so it's better that I unassign myself. /unassign

[TobyTheHutt]

What would be the next steps? We have introduced full parity between Cobra and Kingpin. Kingpin is still the default backend with a hidden switch to test the new Cobra-backend using EXTERNAL_DNS_CLI=cobra ENV-variable or the --cli-backend=cobra flag.

I suggest adding documentation for the new backend, along with an announcement that the default backend will be switched to Cobra at a certain release, if no conflicting feedback comes in. Let me know what you think