Preserve ambiguous merge-base warnings in artifacts

[nia-sg-bot]

Summary

• preserve ambiguous_merge_base as a machine-readable canonical artifact warning
• extend the v2 JSON schema and structural warning allowlist
• add a regression test proving the warning remains schema-valid and actionable

Part of #21.

Remaining work: cover the other requested comparison modes and resolver edge cases from the parent issue.

Summary by CodeRabbit

• Bug Fixes
  • Preserved ambiguous merge-base warnings in generated artifacts, including their warning code and details.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: f2b99176-7ebf-4bc2-ae18-73905a7a9462

📥 Commits

Reviewing files that changed from the base of the PR and between 5fdaebb and 3e427be.

📒 Files selected for processing (3)

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

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

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Walkthrough

The ambiguous_merge_base warning code is now accepted by the schema and warning conversion. A structural test checks that three-dot commit-range resolution preserves the warning code and detail in the artifact.

Changes

Warning preservation

Layer / File(s)	Summary
Accept and preserve resolver warnings diffgraph/schema/diffgraph-v2.schema.json, diffgraph/structural.py, tests/test_structural.py	The schema accepts ambiguous_merge_base, and _resolution_warning no longer maps it to UNKNOWN. The test checks that the artifact retains the warning code and prefixed detail.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 3e427

The artifact now retains ambiguous merge-base warnings as intended, with no remaining merge-blocking issue identified.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 3e427

The change exposes a more specific warning code to JSON consumers without changing comparison execution. Risk appears low, although compatibility with consumers outside this repository has not been verified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — Within the inspected flow, caller-supplied comparison refs can affect which resolver warning is returned, but this PR does not add a route from an ambiguous result to file analysis or a new sensitive operation.

Trust Boundaries and Controls

• observed — The packaged validator still checks warning codes against the schema; the PR adds this specific code to that allowlist rather than removing validation.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files. (1 skipped: 1…	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: preserving ambiguous merge-base warnings in artifacts.
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 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files. (1 skipped: 1 unsupported.)

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✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

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🧪 Generate unit tests (beta)

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