fix: reject symlinked hook directories before mutation

[altaywtf]

Problem

Hook installation rejects a symlinked hook file but follows a symlinked .githooks directory, changing an external file's permissions and configuring Git to execute it.

Solution

Use the existing workspace filesystem boundary before either mutation. Open the validated regular hook without following a final symlink, check its identity, and apply executable permissions through that descriptor. Valid linked worktrees remain supported. Missing hooks keep a distinct diagnostic; missing paths also leave Git configuration unchanged.

Proof

Two new source-CLI parent-symlink regressions failed before the fix: the external hook changed from0600 to0711. The focused suite passes22 tests. The full gate passes165 tests with91.48% aggregate line coverage, unchanged frozen parity, build and installed-tarball smoke. Independent Astra review is clean. Fixtures verify external permissions and both existing/unset Git configuration remain unchanged on rejection. This does not claim isolation from arbitrary concurrent hostile filesystem replacement.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-05T11:41:32.604851Z	46705b6	New commits

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[slopzapper]

✨ CLEAN

hooks install now refuses a symlinked .githooks parent and a symlinked pre-commit before git config or chmod, and the new cases prove both leave the external mode and local Git config untouched.

[Copilot]

🟢 Approval recommended

The change is narrowly scoped, adds targeted regression tests for the identified security/escape scenario, and the updated implementation consistently applies workspace-boundary validation before mutating config or permissions.

Pull request overview

This PR hardens hooks install against symlink-based escape paths by validating the .githooks/pre-commit path within the workspace filesystem boundary before any mutation, and by applying executable permissions through a verified file descriptor to avoid unexpected external permission changes.

Changes:

• Add regression coverage ensuring hooks install rejects symlinked .githooks parents or hook files without mutating Git config or external file permissions.
• Update hook installation to use workspaceLstat for workspace-boundary validation and openSync(...O_NOFOLLOW) + fchmodSync on a verified descriptor for safe permission changes.

File summaries

File	Description
test/hooks.test.ts	Adds regression tests for symlinked parent/hook scenarios and ensures rejection is non-mutating.
src/hooks.ts	Enforces workspace-boundary checks for the hook path and applies executable bits via a verified, non-following file descriptor.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Lite

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[slopzapper]

✨ CLEAN

The change is clean. Hook install now rejects symlink parents and non-regular hook files before git config or chmod, and a missing hook no longer looks like an invalid type.