fix(github): warn on versions host metadata fallback

[jdx]

Summary

• warn when mise-versions GitHub metadata lookups hit rate limits or other non-404 failures
• include the release/attestation lookup context before falling back to the GitHub API
• keep 404 cache misses silent

Why

When mise-versions release metadata fails transiently, mise falls back to the GitHub API. If CI has lost or lacks a GitHub token, the visible failure is a GitHub 403 with no indication that the versions-host lookup failed first. These warnings make that fallback path visible.

Test plan

• cargo fmt
• cargo test versions_host

---

Note

Low Risk
Logging-only change in optional metadata fetch paths; 404 handling and fallback semantics are unchanged.

Overview
Improves visibility when mise-versions GitHub metadata lookups fail and mise silently falls back to the GitHub API.

github_release and github_attestations now pass context-specific labels (e.g. GitHub release metadata for {repo}@{tag}) into shared fetch_optional_json handling. 429 rate limits and other non-404 errors are logged at warn with explicit “falling back” wording instead of debug. 404 responses remain silent (treated as a cache miss).

No change to fallback behavior—only logging and error-message context so CI failures (e.g. GitHub 403 without a token) are easier to trace back to a prior versions-host failure.

^{Reviewed by Cursor Bugbot for commit 77fd1d2. Bugbot is set up for automated code reviews on this repo. Configure here.}

Summary by CodeRabbit

• Chores
  • Enhanced diagnostic logging for rate-limit and lookup failures with more explicit fallback indicators for improved observability.

[coderabbitai]

📝 Walkthrough

Walkthrough

This change improves debugging observability for GitHub API lookups. Two functions now format per-request labels with repository and version information, while the underlying fetch function elevates transient failure messages from debug to warn level, making rate-limit and lookup failures more visible during troubleshooting.

Changes

GitHub API Observability

Layer / File(s)	Summary
Request labels and fallback logging src/versions_host.rs	github_release and github_attestations construct specific labels containing {repo}@{tag} and {repo}@{digest} respectively; fetch_optional_json now logs 429 and non-429 lookup failures at warn! level with "falling back" messaging instead of debug!, while returning Ok(None) on errors.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 Labels now sparkle with specifics clear,
{repo}@{tag} brings debugging cheer!
Warnings now shine where silence once lived,
Better observability the code receives.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: adding warnings when versions host metadata lookups fall back, which is the primary objective of the PR.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/warn-versions-host-metadata-fallback

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[greptile-apps]

Greptile Summary

This PR improves observability in the fetch_optional_json helper by (1) embedding {repo}@{tag} / {repo}@{digest} context in the log label and (2) promoting debug! to warn! for rate-limit and non-404 failures so callers can see when the fallback path to the GitHub API is being taken.

• Labels passed to fetch_optional_json now include the specific repo and tag/digest, making warning messages actionable without needing to enable debug logging.
• Non-404 failures (429 rate-limit and all other errors) now emit warn! instead of debug!, surfacing otherwise-invisible fallback events — especially useful in CI environments without a GitHub token.

Confidence Score: 5/5

Safe to merge — the only behavioral change is promoting two log-level calls from debug to warn, with no mutations to control flow or return values.

The diff is minimal: two label format strings gain context and two debug! macro calls become warn!. Control flow, error propagation, and all Ok(None) / Ok(Some(_)) paths are unchanged. The 404 silent path is explicitly preserved. The new warning text correctly describes the fallback and includes {err:#} for the generic case. No edge cases or regressions are apparent.

No files require special attention.

Important Files Changed

Filename	Overview
src/versions_host.rs	Adds repo/tag context to fetch_optional_json labels and promotes debug→warn for 429 and generic error branches, making the fallback path visible when mise-versions is unavailable.

_{Reviews (1): Last reviewed commit: "fix(github): warn on versions host metad..." | Re-trigger Greptile}

[github-actions]

Hyperfine Performance

mise x -- echo

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.6.0 x -- echo	16.9 ± 0.6	15.7	19.4	1.00
mise x -- echo	17.7 ± 1.7	16.0	47.8	1.04 ± 0.11

mise env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.6.0 env	16.9 ± 0.8	15.5	20.6	1.00
mise env	17.4 ± 0.8	15.8	21.9	1.03 ± 0.07

mise hook-env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.6.0 hook-env	17.5 ± 0.7	16.0	21.9	1.00
mise hook-env	18.1 ± 0.7	16.4	22.5	1.03 ± 0.06

mise ls

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.6.0 ls	14.1 ± 0.7	12.7	17.4	1.00
mise ls	14.5 ± 0.7	13.3	17.9	1.03 ± 0.07

xtasks/test/perf

Command	mise-2026.6.0	mise	Variance
install (cached)	128ms	129ms	+0%
ls (cached)	58ms	58ms	+0%
bin-paths (cached)	60ms	60ms	+0%
task-ls (cached)	120ms	121ms	+0%