Harden unsafe Git option validation

[Byron]

Tasks

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• refackiew

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Everything below this line was generated by Codex GPT-5.

Created by Codex on behalf of Byron. Byron will review before this is ready to merge.

Summary

Harden GitPython's unsafe-option validation against three high-severity advisories affecting GitPython <= 3.1.53:

• GHSA-r9mr-m37c-5fr3: prevent split single-character keyword values from smuggling unsafe option tokens.
• GHSA-6p8h-3wgx-97gf: reject caller-controlled clone templates by default because they can install executable hooks.
• GHSA-fjr4-x663-mwxc: reject diff output options before revision parsing or Git invocation to prevent arbitrary file overwrite.

No CVEs or patched release versions are assigned yet.

Changes

• Validate option-like values emitted when single-character kwargs are split.
• Add --template to the unsafe clone-option denylist.
• Add allow_unsafe_options=False to commit/tree/index diff paths and consistently guard --output/-o.
• Preserve explicit opt-in behavior with allow_unsafe_options=True.
• Add regression coverage for each bypass and affected call path.

Validation

• Focused Python 3.12 security tests: 3 passed.
• Ruff lint and formatting: passed.
• Mypy: passed.
• Full pre-commit suite: passed.
• Full Python 3.12 suite: 667 passed, 75 skipped, 35 unrelated fixture/environment failures caused by uninitialized nested test submodules and local Git defaults.

Git behavior was checked against baseline a23bace9.

[Copilot]

Pull request overview

This PR hardens GitPython’s unsafe Git option validation to block additional high-risk option spellings and close bypasses where unsafe options could be smuggled via argument transformation, while preserving explicit opt-in via allow_unsafe_options=True.

Changes:

• Extend Git._option_candidates() to include option-like values emitted by split single-character kwargs, so unsafe-option checks cover those tokens too.
• Add --template to the clone unsafe-option denylist to prevent hook installation during clone by default.
• Add allow_unsafe_options gating and unsafe-option checks to diff call paths (commit/tree/index) to reject --output/-o unless explicitly allowed, with regression tests.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
git/cmd.py	Expands option-candidate detection to include split single-char kwarg values that look like options.
git/repo/base.py	Adds --template to unsafe_git_clone_options and documents why it’s unsafe.
git/diff.py	Adds allow_unsafe_options and blocks unsafe revision/output options prior to diff invocation.
git/index/base.py	Adds allow_unsafe_options to index diff and enforces unsafe-option checks; propagates flag through delegated diff calls.
test/test_git.py	Adds regression tests ensuring split single-char kwarg values are included in unsafe-option candidate detection.
test/test_diff.py	Adds regression tests ensuring diff output options are rejected by default and allowed only with explicit opt-in.
test/test_clone.py	Extends clone unsafe-option tests to cover --template and template=....

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.