Reduce MCP review latency via shared changed-file resolution and safe cache invalidation

[Bakul2006]

Pull Request

Addressed Review Feedback

Thanks for the detailed review. I've updated this PR to address the concerns raised while preserving the original optimization intent of reducing repeated changed-file detection across MCP review workflows.

What changed

• Added validation for Git refs before subprocess invocation using the existing safe ref checks.

• Routed changed-file resolution through VCS detection to preserve SVN compatibility.

• Avoided caching timeout/empty detection results to prevent cache poisoning across subsequent calls.

• Revisited untracked file handling so newly added files are included in review workflows.

• Resolved merge conflicts against the latest main.

• Added focused unit tests covering:

  • cache hit and expiry behaviour,
  • cache invalidation paths,
  • invalid Git refs,
  • timeout handling,
  • SVN compatibility,
  • untracked file handling.

Original intent preserved

This optimization is still designed specifically for short-lived MCP review orchestration bursts where multiple tools execute against effectively identical repository state.

The goal remains to avoid repeated changed-file detection during multi-tool review flows while failing fast when automatic detection is slow.

Validation

• Rebased/merged with the latest main.
• Resolved the reported conflicts.
• Verified the updated test suite after conflict resolution.

Thanks again for the review and guidance. I'd appreciate another pass whenever you have time.

Linked issue

#457

Closes #457

What & why

How it was tested

uv run pytest tests/ --tb=short -q
uv run ruff check code_review_graph/
uv run mypy code_review_graph/ --ignore-missing-imports --no-strict-optional

Checklist

• Tests added for new functionality
• All tests pass: uv run pytest tests/ --tb=short -q
• Linting passes: uv run ruff check code_review_graph/
• Type checking passes: uv run mypy code_review_graph/ --ignore-missing-imports --no-strict-optional
• Lines are at most 100 characters
• Docs updated where behavior changed (README, docs/, docstrings)