ENG-1118: Review individual commits in PR sidebar

[arnestrickmann]

Summary

• Adds expandable commit rows in the PR commits sidebar.
• Shows changed files for each expanded commit and opens them in the existing diff viewer.
• Generalizes fixed git ref-to-ref diffs so commit file diffs compare parent commit to commit instead of HEAD.
• Keeps PR file diffs, image/binary handling, prefetching, and line comments on the existing diff infrastructure.

Validation

• pnpm run format
• pnpm run typecheck
• pnpm run lint
• pnpm run test

[greptile-apps]

Greptile Summary

This PR adds expandable commit rows to the PR sidebar, showing per-commit file diffs that open in the existing Monaco diff viewer. It generalises the modifiedRef pattern (previously 'pr'-only) to 'git' group diffs and replaces the old path+group-only tab deduplication with a ref-aware _findDiffEntry so commit diffs for the same file in different commits coexist as separate tabs.

• Commit file lists are loaded via a new useCommitFiles hook; diffs use a parent^→commit ref pair passed through the full diff stack (DiffSlotStore, StackedDiffPanel, diff-file-renderer, prefetch hook).
• _findDiffEntry in TabManagerStore now validates originalRef and modifiedRef (via value-based refsEqual) in addition to path and group, preventing incorrect tab reuse across different commit diffs.
• GitChangeStatus replaces string in CommitFile.status and statusMap, tightening the type contract between the git service and the renderer.

Confidence Score: 5/5

Safe to merge; the ref-generalisation is applied consistently across the diff stack and the new tab-lookup logic correctly scopes commit diffs by value-compared refs.

All changed code paths fall back correctly to HEAD_REF for existing working-tree 'git' diffs, preserving prior behaviour. The new _findDiffEntry uses value-equality (refsEqual) rather than reference equality, so ref objects reconstructed from state remain comparable. No cross-cutting regressions were identified.

No files require special attention beyond the minor suggestions already noted.

Important Files Changed

Filename	Overview
src/renderer/features/tasks/diff-view/changes-panel/components/pr-entry/commits-list.tsx	Adds expandable commit rows with file lists; replaces virtualizer with flat map and toggle-expand state. useMemo uses the full commit object as a dependency, causing originalRef/modifiedRef to be recreated every time a new page is fetched.
src/renderer/features/tasks/diff-view/changes-panel/components/pr-entry/use-commit-files.ts	New hook that fetches changed files for a commit; projectId is missing from the query key (previously flagged).
src/renderer/features/tasks/tabs/tab-manager-store.ts	Replaces path+group-only tab deduplication with ref-aware lookup (_findDiffEntry), correctly scoping commit diffs by both originalRef and modifiedRef using value-based refsEqual comparisons.
src/renderer/features/tasks/diff-view/main-panel/stacked-diff-view.tsx	Propagates modifiedRef for 'git' group slots; contains a redundant ternary inside StackedFileSlot whose false branch is unreachable dead code.
src/renderer/features/tasks/diff-view/stores/stacked-diff-panel-store.ts	Makes modifiedUri for 'git' group use this.modifiedRef ?? HEAD_REF instead of hard-coded HEAD_REF, enabling commit-scoped diffs while preserving working-tree behaviour via the fallback.
src/renderer/features/tasks/diff-view/changes-panel/hooks/use-prefetch-diff-models.ts	Extends the effectiveModifiedRef shortcut from 'pr'-only to both 'git' and 'pr' groups; logic is consistent with the rest of the PR.
src/shared/git.ts	Tightens CommitFile.status from string to GitChangeStatus — a type-safety improvement with no runtime impact.
src/shared/view-state.ts	Updates modifiedRef JSDoc to reflect that it now applies to both 'git' and 'pr' groups.
src/main/core/git/impl/git-service.ts	Tightens statusMap type from Map<string, string> to Map<string, GitChangeStatus>, consistent with the shared-type change.

Sequence Diagram

sequenceDiagram
    participant Sidebar as PrCommitsList
    participant CommitItem
    participant FilesList as CommitFilesList
    participant Hook as useCommitFiles
    participant Prefetch as usePrefetchDiffModels
    participant TabMgr as TabManagerStore
    participant Renderer as diff-file-renderer

    Sidebar->>CommitItem: render commit row
    CommitItem->>CommitItem: toggle expandedHashes on click
    CommitItem->>FilesList: "mount (isExpanded=true)"
    FilesList->>Hook: useCommitFiles(projectId, workspaceId, hash)
    Hook-->>FilesList: GitChange[]
    FilesList->>Prefetch: usePrefetchDiffModels('git', commitRef(hash^), commitRef(hash))
    Note over FilesList: originalRef = commitRef("hash^")<br/>modifiedRef = commitRef("hash")
    FilesList->>TabMgr: "openDiffPreview({group:'git', originalRef, modifiedRef})"
    TabMgr->>TabMgr: _findDiffEntry — match path + group + refsEqual(originalRef) + optionalRefsEqual(modifiedRef)
    TabMgr-->>Renderer: activate DiffTabStore
    Renderer->>Renderer: "modifiedUri = toGitUri(uri, tab.modifiedRef ?? HEAD_REF)"

Loading

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
src/renderer/features/tasks/diff-view/main-panel/stacked-diff-view.tsx:183-185
The inner ternary's condition (`diffType === 'git' || diffType === 'pr'`) is always `true` inside the enclosing `else if (diffType === 'git' || diffType === 'pr')` block, so the `: HEAD_REF` branch is dead code. Simplifying to `modifiedRef ?? HEAD_REF` removes the redundancy.

```suggestion
    } else if (diffType === 'git' || diffType === 'pr') {
      const effectiveModifiedRef = modifiedRef ?? HEAD_REF;
```

### Issue 2 of 2
src/renderer/features/tasks/diff-view/changes-panel/components/pr-entry/commits-list.tsx:149-150
`data.pages.flat()` rebuilds the entire `commits` array on every page fetch, giving each element a fresh object identity even when its content is unchanged. Because `useMemo` compares dependencies by reference, `originalRef` and `modifiedRef` are recreated for every expanded `CommitFilesList` on each page load, which in turn invalidates the `useCallback` in `usePrefetchDiffModels`. Since both computations only read `commit.hash`, using that as the sole dependency keeps the memoised values stable across pagination.

```suggestion
  const originalRef = useMemo(() => parentRefForCommit(commit), [commit.hash]);
  const modifiedRef = useMemo(() => commitRefForCommit(commit), [commit.hash]);
```

_{Reviews (2): Last reviewed commit: "ENG-1118: Review individual commits in P..." | Re-trigger Greptile}

[arnestrickmann]

@greptileai @greptile

[arnestrickmann]

Tested the updated comment scoping with a PR that has two commits touching the same file: src/renderer/features/command-palette/command-palette-modal.tsx.

I added one draft line comment in each commit diff, then injected the comments into the agent context.
The resulting context now emits two separate commit-scoped targets instead of grouping by file path only:

This shows each comment is attached to the specific commit diff where it was written, even though both comments are on the same file path.

<user_comments>
  <target kind="commit" originalSha="e229a6d960ec82b3f9eb29dbfe50ab2a4b00a509"
    modifiedSha="12e6cd36c123ed61268e546c1ba8215584dfe404"
    path="src/renderer/features/command-palette/command-palette-modal.tsx">
    <comment line="1">test</comment>
  </target>
  <target kind="commit" originalSha="93ed50e064ce6573b3d946da0af588c1db2bf2c2"
    modifiedSha="ef44918580cf4e14d84ddcbbb70ca8636ba62023"
    path="src/renderer/features/command-palette/command-palette-modal.tsx">
    <comment line="3">test</comment>
  </target>
</user_comments>

[arnestrickmann]

lfg