fix(git): warn on undecodable path bytes

[nia-sg-bot]

Summary

• reject non-UTF-8 Git path bytes before they can leak surrogate escapes into JSON artifacts
• preserve subsequent valid snapshot records and expose an actionable undecodable_path warning
• register the warning in the structural schema and cover resolver/schema behavior

Part of #21

Validation

• python3 -m pytest -q (139 passed)
• git diff --check

Remaining for #21

• complete the broader comparison-mode and edge-case fixture coverage described in the parent issue.

Summary by CodeRabbit

• Bug Fixes

  • Git snapshots now handle filenames that cannot be decoded as UTF-8 without stopping the entire scan.
  • Invalid paths are skipped individually, while valid files continue to appear normally.
  • Added clear undecodable_path warnings without exposing escaped or malformed filenames.

• Schema

  • Added support for machine-readable undecodable_path warnings in artifact metadata.

[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: 8f0a488c-7deb-4e39-96a0-dbf94d9f5ba1

📥 Commits

Reviewing files that changed from the base of the PR and between 5e7a307 and d71cf3c.

📒 Files selected for processing (5)

• diffgraph/git_snapshot.py
• diffgraph/schema/diffgraph-v2.schema.json
• diffgraph/structural.py
• tests/test_git_snapshot.py
• tests/test_structural.py

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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Walkthrough

Git path parsing now uses strict UTF-8 decoding. Invalid paths produce undecodable_path warnings and are skipped without stopping parsing. The warning is included in the JSON schema and preserved in structural artifact output.

Changes

Undecodable Git path handling

Layer / File(s)	Summary
Git path decoding and scoped skipping diffgraph/git_snapshot.py, tests/test_git_snapshot.py	Raw diff and untracked paths use strict UTF-8 decoding. Invalid paths produce escaped undecodable_path warnings and are skipped individually. Tests verify that valid files remain in the result.
Warning propagation and validation diffgraph/structural.py, diffgraph/schema/diffgraph-v2.schema.json, tests/test_structural.py	Structural output preserves undecodable_path warnings. The schema accepts the new code. Tests verify schema-valid output without a file field when none is provided.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to d71cf

The change rejects undecodable Git paths before serialization, emits a structured warning, and preserves valid records; 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 27.27% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 4 files. (1 skipped: …	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 summarizes the main change: Git now warns when it encounters undecodable path bytes.
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 27.27% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 4 files. (1 skipped: 1 unsupported.)

• 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-undecodable-paths

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[nia-sg-bot]

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