feat: robust upgrade detection — non-interactive git, auth injection, 24h cache

[ericchansen]

Summary

Makes plugin upgrade detection robust for all users, including non-developers with private repos and multi-account setups. Based on patterns from Homebrew, pip, npm, gh CLI, k9s, and Renovate.

Non-interactive git (_git_env)

• GIT_TERMINAL_PROMPT=0 — git never hangs waiting for credentials
• GIT_SSH_COMMAND with -oBatchMode=yes — kills SSH passphrase prompts
• Auto-injects GitHub token via gh auth token using Renovate-style GIT_CONFIG_COUNT env vars (zero files touched)
• Falls back silently if gh is not installed or not authenticated

Graceful fetch fallback

• Auth failures no longer abort — falls back to local cached tags from previous successful fetches
• New _cached_latest parameter on check_plugin() allows skipping network entirely when cache is fresh

24h disk cache (UpgradeCache)

• New ~/.copilot/upgrade-cache.json with per-plugin {latest_version, checked_at}
• 24h TTL (matches gh CLI). Press r to force refresh.
• Thread-safe, atomic writes via existing write_json() with .bak rotation
• Cache invalidated automatically after successful copilot plugin update
• Corrupted/missing cache handled gracefully

Tests

• _git_env(): terminal prompt, SSH batch mode, token injection via env vars, no-gh fallback
• _cached_latest: cache hit skips fetch, up-to-date detection
• Fetch failure fallback to local tags
• UpgradeCache: set/get, TTL expiry, invalidation, corruption, schema mismatch, multi-plugin independence

[Copilot]

Pull request overview

This PR improves plugin upgrade detection robustness by making git operations non-interactive, adding GitHub auth token injection support, and introducing a 24-hour disk cache to reduce network calls and failures for end users.

Changes:

• Add _git_env() and route all git subprocess calls through it to avoid interactive prompts and optionally inject GitHub auth via GH_TOKEN/GITHUB_TOKEN or gh auth token.
• Add a disk-backed UpgradeCache (~/.copilot/upgrade-cache.json) with TTL-based reads and graceful handling for missing/corrupt cache.
• Update the Plugins tab to use the cache for background upgrade checks and invalidate cache entries after successful plugin upgrades; add tests for cache and new upgrade-detection behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/copilotsetup/plugin_upgrades.py	Adds non-interactive/auth-aware git env and adds cached-latest + fetch-fallback behavior in check_plugin().
src/copilotsetup/upgrade_cache.py	New disk-backed cache wrapper around check_plugin() with TTL and schema validation.
src/copilotsetup/tabs/plugins.py	Switches plugin upgrade detection to use UpgradeCache and invalidates cache after upgrades.
src/copilotsetup/config.py	Adds upgrade_cache_json() path helper for cache location.
tests/test_plugin_upgrades.py	Adds unit tests for _git_env(), _cached_latest, and fetch-failure fallback behavior.
tests/test_upgrade_cache.py	Adds tests covering cache load/reset behavior, TTL, invalidation, and multi-plugin entries.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.