tests: scrub inherited git env pointers at package import

[sumitake]

Summary

Defense-in-depth follow-up to #86, operator-directed: tests/__init__.py now scrubs inherited per-repo git environment pointers (GIT_DIR, GIT_WORK_TREE, GIT_INDEX_FILE, GIT_PREFIX, GIT_OBJECT_DIRECTORY, GIT_ALTERNATE_OBJECT_DIRECTORIES, GIT_COMMON_DIR) at package import — so every runner of the suite is safe from the incident class (hook-inherited absolute GIT_DIR making temp-dir git calls mutate the real .git/config), not just the sanitized pre-push wrapper.

Scoping decisions (each verified or reasoned in the diff comment):

• GIT_CONFIG_GLOBAL/GIT_CONFIG_SYSTEM deliberately untouched — temp-repo commits rely on machine identity.
• scripts/ root deliberately untouched — namespace package (no __init__ to ride) AND empirically unexposed: 327/327 pass under a poisoned absolute GIT_DIR with zero config writes.
• Tests that deliberately exercise poisoned git env must set variables after package import (documented in the comment; the hooks: full-suite pre-push test gate (both unittest roots, git-env sanitized) #86 wrapper test already does this via subprocess env).

Regression tests (2, in tests/test_git_env_hardening.py): in-process absence of all seven pointers, and a freshly-poisoned child interpreter whose import tests must scrub them all.

Verification: the incident reproduction (poisoned absolute GIT_DIR → 23 errors) now runs 658/658 green with zero config mutation; clean runs unaffected (660/660 with the new tests; 327/327 scripts). Test infrastructure only — no version bump; changelog fragment included.

Cross-check (verbatim)

Codex (gpt-5.6-sol, effort low, direct codex exec under operator broker-bypass authorization):

PROCEED

Concerns (all integrated): document that poisoned-env tests must set variables post-import — added to the comment; regression test asserting variable absence — added (both in-process and child-import forms); global-config exclusion and scripts/ exclusion judged justified as scoped.

author: claude
author_model: claude-fable-5 (effort: default)
standing_directives: operator-directed follow-up (2026-08-03 "Proceed with the test-setUp git-env hardening"); directive #9 defense-in-depth for ledger plugin.tests.inherit.git.hook.env.mutate.real.repo; #7 model+effort stated; #8 no fan-out
tier: 2
cross_check: PROCEED (codex gpt-5.6-sol, effort low, direct codex exec under operator broker-bypass authorization 2026-08-03; raw verdict quoted in PR body; both actionable concerns integrated)
post_condition: 660/660 + 327/327 tests OK; incident reproduction now green (was 23 errors) with zero config mutation; changelog dry-run OK; push traversed the #86 gate
mcp_coverage_gap: none — test infrastructure; gemini_mcp_path: retired / not applicable
contributor_rights: OWNER-AUTHORED
operator_reserved: no
plugin_affected: NONE — test infrastructure, no distributed plugin content
readme_refresh_status: README unaffected (no release, no version bump)

🤖 Generated with Claude Code

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[chatgpt-codex-connector]

Scrub GIT_CONFIG before running temp-repo commands

When the suite inherits GIT_CONFIG=/path/to/config, this allowlist leaves it active, so temp-repository calls such as PublicExportSafetyTests._init() running git config user.email/user.name silently modify that external file rather than the temporary repo. This reproduces the configuration-corruption class the change is intended to prevent; Git 2.43 also includes GIT_CONFIG in git rev-parse --local-env-vars, and the official documentation says it takes configuration from the named file instead of .git/config (Git documentation). Add GIT_CONFIG to the scrubbed variables while continuing to preserve the intentionally retained global/system settings.

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