Replace Flags library alecthomas/kingpin with spf13/pflag

[ivankatliarchuk]

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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 Although it offers a great developer experience, it is archived and no longer maintained.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

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📦 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