fix: normalize rename-only diff paths

[benvinegar]

Summary

• strip parser-added trailing newlines from parsed diff paths
• normalize rename-only labels in loaders, file labels, and the OpenTUI diff adapter
• add regression coverage for cross-directory pure renames

Problem

@pierre/diffs can return prevName with a trailing newline for pure rename patches. That made Hunk render rename-only headers inconsistently, including cases where the old path and -> new/path appeared on separate lines instead of one old/path -> new/path header.

Testing

• bun run typecheck
• bun test
• bun run test:tty-smoke

This PR description was generated by Pi using OpenAI GPT-5

[greptile-apps]

Greptile Summary

This PR fixes a rendering bug where @pierre/diffs returns prevName with a trailing newline for pure rename patches, causing the old path and -> new/path to appear on separate header lines. The fix centralizes path sanitization in a new diffPaths.ts helper and applies it consistently at the loader, OpenTUI adapter, and UI helper layers, with targeted regression coverage.

Confidence Score: 5/5

Safe to merge — targeted bug fix with no logic regressions and good test coverage at both integration and unit levels.

All findings are P2 or lower. Normalization is applied at the right layers (source in the loader, defensively in UI helpers and the OpenTUI adapter). The early-return optimization in normalizeDiffMetadataPaths is correct. Regression coverage covers both the end-to-end loader path and the standalone UI helper path.

No files require special attention.

Important Files Changed

Filename	Overview
src/core/diffPaths.ts	New helper module introducing normalizeDiffPath and normalizeDiffMetadataPaths; clean implementation with efficient early-return when no normalization is needed.
src/core/loaders.ts	Applies normalizeDiffMetadataPaths in buildDiffFile and normalizeDiffPath in findPatchChunk and resolvedPreviousPath; normalization is now at the source so all downstream consumers receive clean paths.
src/core/loaders.test.ts	Adds an integration regression test for a cross-directory pure rename patch verifying that both path and previousPath are free of trailing newlines end-to-end.
src/opentui/HunkDiffView.tsx	Adds normalization in toInternalDiffFile so the public OpenTUI component adapter also strips trailing newlines from paths received from external callers.
src/ui/lib/files.ts	Adds defensive normalizeDiffPath calls in sidebarFileName, fileLabelParts, filterReviewFiles, and buildSidebarEntries to handle any DiffFile objects that arrive with non-normalized paths.
src/ui/lib/files.test.ts	Adds unit test for fileLabelParts with a raw \n-suffixed previousPath, directly exercising the defensive normalization in the UI helpers.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["@pierre/diffs parsePatchFiles()\nreturns prevName with \\n"] --> B["loaders.ts buildDiffFile()\nnormalizeDiffMetadataPaths()"]
    B --> C["DiffFile.path / previousPath\n(clean, no trailing newlines)"]
    C --> D["files.ts UI helpers\nsidebarFileName / fileLabelParts\n(defensive normalizeDiffPath)"]
    C --> E["App renders correct\nold/path -> new/path header"]
    F["HunkDiffView.tsx (OpenTUI)\nExternal diff input"] --> G["toInternalDiffFile()\nnormalizeDiffMetadataPaths()\nnormalizeDiffPath()"]
    G --> C
    H["findPatchChunk()\npath matching"] --> I["normalizeDiffPath on candidates\nbefore chunk lookup"]

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