fix(index): pass a Windows hook outside the work tree by absolute path

[6801318d8d]

This PR was written by Claude Code, an AI agent, on behalf of the account owner.

Fixes #2287.

On Windows, a hook found through a core.hooksPath outside the working tree is passed to Bash by a path relative to the working tree. Git for Windows mounts the user's temporary directory as /tmp, so from a repository under %TEMP% that relative path leads elsewhere in Bash, and the hook fails with exit code 127 (details in #2287).

Change

In run_commit_hook (git/index/fun.py):

• A relative path inside the working tree is kept: it cannot cross a mount point.
• A relative path leaving the working tree (starting with ..) is replaced by the absolute path in POSIX form (C:/...), as is already done for a hook on another drive, when the Bash is Git for Windows' own or one found on PATH: both accept it.
• The bare bash.exe fallback, which may be the WSL launcher and cannot open a Windows absolute path, keeps the relative path as before.

Tests

• test_run_commit_hook_outside_worktree_on_windows now checks the command for the three cases. Its first assertion (outside the working tree, Git for Windows' Bash) fails without the change.
• test_pre_commit_hook_outside_worktree runs a real hook through a core.hooksPath outside the working tree.

Validation

On Windows 11 with Git for Windows 2.50.1 and Python 3.14:

• test/test_index.py with an empty global Git configuration: 183 passed, 3 skipped, 1 xpassed (182 passed on main; the xpass is test_commit_msg_hook_success, as on main).
• ruff 0.16.9 (check and format) and mypy on the changed files: no issues.
• A commit in a repository under %TEMP% with a global core.hooksPath holding a pre-commit hook succeeds; on main it fails with exit code 127.

Not run here: Linux and macOS (the command-construction test mocks sys.platform, so CI runs it there too) and a WSL bash.exe.

A related observation, outside the scope of this PR: with a global core.hooksPath set, some hook tests in test/test_index.py (for example test_pre_commit_hook_fail and test_commit_msg_hook_fail) fail even with this change, because they expect the hook from the repository's own hooks directory while Git's configuration points elsewhere. They pass with an empty global configuration.

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

The focused fix preserves existing fallback behavior, includes regression coverage, and has no identified blocking issues.

0 open findings

What changed in this PR

This PR fixes Windows hook execution when core.hooksPath points outside a working tree under %TEMP%, addressing #2287.

Review by GitHub Copilot.

Changes:

• Pass outside-worktree hooks by absolute POSIX-form path to discovered Bash executables.
• Preserve relative paths for internal hooks and the bare bash.exe fallback.
• Expand command-construction coverage and add an external-hook integration test.

File	Description
test/​test_index.py	Tests path selection and external-hook execution.
git/​index/​fun.py	Adjusts Windows hook paths while preserving fallback behavior.

🧠 Review effort: Balanced

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[Byron]

Double checked with Codex on Windows, and WSL support as well.