Fix commit hooks to respect core.hooksPath configuration

[MirrorDNA-Reflection-Protocol]

Summary

Fixes #2083

The run_commit_hook() function was hardcoded to look for hooks in $GIT_DIR/hooks, ignoring the core.hooksPath configuration option that Git has supported since v2.9.

Changes

• Add _get_hooks_dir() helper function that reads core.hooksPath from config
• Handle both absolute and relative paths per git-config documentation:
  • Absolute paths: used as-is
  • Relative paths: resolved relative to the working tree root (or git_dir for bare repos)
  • Not set: defaults to $GIT_DIR/hooks
• Update run_commit_hook() to use the new helper
• Add comprehensive tests for both absolute and relative hooksPath configurations

Testing

• All existing hook tests pass
• Added 2 new tests:
  • test_run_commit_hook_respects_core_hookspath - tests absolute path
  • test_run_commit_hook_respects_relative_core_hookspath - tests relative path

Backwards Compatibility

The existing hook_path() function is preserved for backwards compatibility and has been documented to note that it does not respect the config. Code that directly uses hook_path() will behave as before. Only code using run_commit_hook() (including index.commit()) will benefit from the new behavior.

References

• Git documentation on core.hooksPath: https://git-scm.com/docs/git-config#Documentation/git-config.txt-corehooksPath
• Issue: https://github.com/gitpython-developers/GitPython/issues/2083