test(git): preserve executable mode provenance

[nia-sg-bot]

Summary

• add deterministic resolver coverage for executable-bit-only changes
• verify unstaged and staged snapshots preserve the exact pre/post modes
• verify mode-only transitions retain the same immutable blob ID at both endpoints

Part of #21.

Validation

• python3 -m pytest tests/test_git_snapshot.py -q (19 passed)
• python3 -m pytest -q (134 passed)
• git diff --check

Remaining work

#21 still needs any remaining comparison edge-case slices beyond executable-mode provenance.

Summary by CodeRabbit

• Tests
  • Added coverage confirming executable-permission changes preserve exact file content provenance.
  • Verified that both staged and unstaged changes report the correct file modes and matching content identifiers.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 4a5ddb71-bd56-41be-94fb-b3cc55210ff9

📥 Commits

Reviewing files that changed from the base of the PR and between 0a8a0e4 and b45c60e.

📒 Files selected for processing (1)

• tests/test_git_snapshot.py

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Walkthrough

Adds a test for executable-bit-only changes. The test verifies that staged and unstaged resolution reports both file modes and preserves the original blob OID at both endpoints.

Changes

File mode provenance

Layer / File(s)	Summary
Mode transition resolution test tests/test_git_snapshot.py	Adds coverage for 100644 to 100755 changes. The test checks the reported modes and identical old_oid and new_oid values for staged and unstaged resolution.

Estimated code review effort: 2 (Simple) | ~5 minutes

Merge Risk: ⚪ Minimal · up to b45c6

This change adds regression tests for preserving executable-file modes and blob identity without changing production behavior. No actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding Git tests for preserving executable-mode provenance.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch nia/issue-21-file-mode-provenance

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[nia-sg-bot]

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