Make the verdict-review-gate and claude-lane tests hermetic against global git hooks - #204

Summary

This finishes the job #181 started (Fixes #179 there). On a host with a global core.hooksPath and ignore file, as the agent-ecosystem-managed ~/.config/git has, clean main fails locally:

• 46 errors in tests.test_verdict_review_gate
• 1 failure in tests.test_claude_lane

CI runners have no global git config, so CI stays green. The global hook stays strict. This PR adds no hook exemption; it fixes the tests.

Causes

• test_verdict_review_gate
  • GateFixture.git and the read-tracer subprocess drop every inherited GIT_* variable. That includes the GIT_CONFIG_GLOBAL / GIT_CONFIG_NOSYSTEM that Make tests hermetic against global and system git config #181 sets.
  • As a result, fixture commits read the developer's global config and ran its gitleaks pre-commit hook. The hook flagged synthetic digests as generic-api-key, for example "packet_keys_sha256" in the scratch run-manifest.json, and blocked 46 fixture commits.
  • The gate's own git_environment() drops those variables too. So gate.main --head also ran the global post-checkout hook in its head worktree; a failing hook there fails git worktree add.
• test_claude_lane: not a hook.
  • Its git calls inherit Make tests hermetic against global and system git config #181's environment. But git reads $XDG_CONFIG_HOME/git/ignore (~/.config/git/ignore) as the default core.excludesFile, and GIT_CONFIG_GLOBAL does not change that.
  • The managed ignore file lists .claude/settings.local.json. So claude_lane.py's git status --porcelain -- .claude … did not see the test's local settings file and returned 0 instead of 2.

Changes

• tests/__init__.py
  • The hermetic global file now sets core.excludesFile and core.attributesFile to /dev/null. These are the two XDG defaults that GIT_CONFIG_GLOBAL does not replace.
  • New hermetic_git_environment(): os.environ without inherited GIT_* routing variables, with the hermetic configuration applied again.
• tests/test_verdict_review_gate.py
  • GateFixture.git and trace() use hermetic_git_environment().
  • GateFixture.setUp patches gate.git_environment with it, so the gate's own git calls on the scratch repository are hermetic too, including worktree add. Routing variables are still dropped.
  • Production code (scripts/verdict_review_gate.py, claude_lane.py) is unchanged.
• tests/test_hermetic_git.py
  • Adds a reusable hostile_home() fixture: every hook exits 1 via ~/.gitconfig and $XDG_CONFIG_HOME/git/config, the ignore file is *, and the attributes file is * hostile.
  • Asserts that scratch repositories are unaffected by it. A non-vacuous control shows that a git which reads it ignores the file, sets the attribute and cannot commit.
  • Asserts that hermetic_git_environment() drops GIT_DIR / GIT_INDEX_FILE and keeps the hermetic config.
  • Runs test_head_revision_is_checked_in_a_temporary_worktree and the claude-lane BIND-R4-8 test under the hostile HOME.
• manifests/evidence.json: new sha256 and byte count for tests/__init__.py only.

Local reproduction

Environment: macOS arm64, Apple Git 2.50.1, Python 3.13.15. Command:

uv run --no-project --python 3.13 python -m unittest tests.test_verdict_review_gate tests.test_claude_lane tests.test_hermetic_git

The two new module-level hostile tests fail against main's tests/__init__.py and gate test module, and pass on this branch:

• Gate: git init is aborted by the hostile reference-transaction hook.
• claude-lane: nothing to commit under the hostile ignore file.

Other checks, all local:

• scripts/validate.py passed.
• gitleaks 8.30.1 with .gitleaks.toml over origin/main..HEAD: no leaks. The commit also passed the strict global pre-commit guard.
• Full python -m unittest on this branch (rebased on 149940a): 4324 tests, 522 skipped, 1 failure. The failure is test_adoption_bootstrap_macos…test_install_path_with_shell_syntax_is_data_in_the_wrapper. It fails the same way with main's tests/__init__.py: SIP strips DYLD_LIBRARY_PATH through /bin/sh on this Mac, so it predates and is unrelated to this change.

Follow-ups (not in this PR)

• claude_lane.py's BIND-R4-8 check (git status --porcelain -- .claude CLAUDE.md AGENTS.md) honours the operator's global excludes. On a host whose ~/.config/git/ignore lists .claude/settings.local.json, a local settings file in the agent-lab checkout is therefore not reported. The check may want --ignored, or an explicit core.excludesFile.
• tests/test_workflow_hardening.py and tests/test_osv_lockfile_coverage.py use the same GIT_*-stripping idiom and pass here. They can adopt hermetic_git_environment() separately.

Refs #179, #181

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