Support i18n / localized output (Chinese, Japanese, German)

[tiulpin]

Area

Other / Not sure (cross-cutting — affects all user-facing output)

Problem or use case

The CLI is English-only. Some users prefer localized human-prose output (errors, hints, help text, table headers, status messages).

This issue is intentionally a placeholder for upvotes / discussion. We do not plan to implement i18n unless there is clear demand. Most popular dev/cloud CLIs (gh, kubectl, docker, aws, gcloud, terraform, even Alibaba/Tencent/Huawei cloud CLIs) ship English-only, so the bar for taking this on is high.

If you want this, please react with 👍 on this issue and (optionally) leave a comment with:

• Which language(s) matter to you
• Whether you'd be willing to contribute / review translations

Proposed solution

If we proceed, the shape would roughly be:

Languages (initial scope, in priority order):

1. English (source of truth)
2. Chinese — Simplified (zh_CN)
3. Japanese (ja)
4. German (de)

Additional locales only if community contributors volunteer to maintain them.

Mechanics:

• github.com/nicksnyder/go-i18n/v2 for message catalogs (TOML files under internal/i18n/)
• Locale resolution: LC_MESSAGES → LANG → fallback to English
• English fallback is mandatory — missing keys never surface as raw IDs

Translate:

• Error messages, hints, suggestions
• Help text (long descriptions, flag usage)
• Table column headers, status labels, prompts

Never translate:

• Command names, flag names, subcommand names
• JSON keys and values (machine-readable output stays stable)
• Enum values returned by the API (SUCCESS, FAILURE, RUNNING, …)
• Log levels, env var names, URLs
• Anything that users grep or pipe in scripts/CI

Alternatives considered

• Do nothing (current state) — matches every popular dev CLI; lowest maintenance cost.
• Docs-only localization — translate docs/topics/ without touching CLI output. Lower risk, partially addresses the gap, doesn't break script compatibility.
• More languages upfront (es, fr, ko…) — rejected for initial scope; translation churn on a fast-moving CLI tends to leave secondary locales stale.

[purrtc0l]

I'm interested in providing Simplified Chinese (zh_CN) support. Would love to translate the CLI strings as well as the docs/topics/ documentation and provide ongoing reviews.