code-go-git

Idiomatic review checklist for go-git v5 concurrent access patterns.

MUST FIX

1. [SAFETY] *git.Repository is NOT goroutine-safe — a per-repo sync.Mutex (not sync.RWMutex) is required for all access. Issue #773 is open as of v5.18.
2. [SAFETY] The packfile MemoryIndex has a confirmed concurrent-map crash (fatal error: concurrent map read and map write) triggered by concurrent repo.Log() / CommitObject on the same repo. Issue #1121, June 2024, unfixed in v5.x.
3. [SAFETY] repo.Log(), CommitObject(), and all iterator types are NOT safe to call concurrently on the same *git.Repository.
4. [CONCURRENCY] repo.Worktree() / wt.Status() wraps the same underlying object storage — calling concurrently on the same repo is unsafe.
5. [CONCURRENCY] The per-repo mutex must cover the full iterator lifetime, not just the initial API call. Iterators lazily read from shared object storage on each Next() — releasing the lock between obtaining an iterator and exhausting it is a data race.
6. [CONCURRENCY] sync.RWMutex does NOT help — go-git "read" operations mutate internal maps (object cache, MemoryIndex). Use sync.Mutex only.
7. [SAFETY] v5.17.0 added extension validation: git.PlainOpen now returns errors for repos with unsupported extensions. Errors from PlainOpen must propagate; never store a nil repo.
8. [ANTI-PATTERN] Never cache a CommitIter or ObjectIter across calls — iterators hold internal cursor state over shared storage. Create and fully drain within one mutex-protected window.
9. [ANTI-PATTERN] Never cache a *Worktree in a long-lived struct — it holds a snapshot of the HEAD/filesystem state and becomes stale after git fetch or index changes.
10. [ANTI-PATTERN] Never call git.PlainOpen while holding the per-repo mutex — PlainOpen reads .git/config, HEAD, and packed-refs from disk (I/O-bound). Open outside the lock, then store via sync.Map.LoadOrStore.
11. [CONCURRENCY] Concurrency fixes for CommitObjects().Foreach() and related iterators are v6-exp only and NOT backported to v5. There is no "safe subset" of go-git v5 that is natively goroutine-safe for shared-repo reads.

SUGGEST