Walkthrough

This pull request introduces diff visualization capabilities by adding a diff package dependency, creates new showDiff and globalReplace utilities for contextualized patch diffing with optional unchanged content display, refactors patch files to use these utilities, adds a --show-unchanged CLI flag, enhances whitespace preservation in system prompt synchronization, and removes verbose diagnostic logging from patch operations.

Changes

Sequence Diagram

sequenceDiagram
    participant CLI as CLI Interface
    participant Utils as Feature Flags<br/>(utils.ts)
    participant Patch as Patch Operation
    participant GlobalReplace as globalReplace()
    participant ShowDiff as showDiff()
    participant Console as Console Output

    CLI->>Utils: --show-unchanged flag received
    Utils->>Utils: enableShowUnchanged()<br/>(set isShowUnchangedOn = true)
    Patch->>GlobalReplace: Call globalReplace(content, pattern, replacement)
    GlobalReplace->>GlobalReplace: Collect all matches<br/>(preserve indices)
    GlobalReplace->>GlobalReplace: Apply replacements<br/>in reverse order
    GlobalReplace->>ShowDiff: For each replacement:<br/>showDiff(old, new, ...)
    ShowDiff->>ShowDiff: Check isShowUnchanged()<br/>and isVerbose()
    alt Verbose Mode Enabled
        ShowDiff->>ShowDiff: Compute word-level diff<br/>with Unicode normalization
        ShowDiff->>ShowDiff: Build context window<br/>around change
        ShowDiff->>Console: Output colored diff<br/>(red for removals,<br/>green for additions)
    end
    GlobalReplace-->>Patch: Return modified content

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

The review requires careful examination of new patchDiffing.ts logic (281 lines) including Unicode normalization, diff computation, and context windowing. Multiple interdependent changes span CLI, patch infrastructure, whitespace handling, and utilities. While many changes follow consistent patterns, the density of algorithmic logic in showDiff() and globalReplace(), plus coordination across multiple files, warrants substantial attention.

Possibly related PRs

• Enhance show diff #420: Directly modifies showDiff() display behavior and context rendering — overlaps with the core diffing implementation introduced here.
• Don't trim newlines when reading system prompt markdown files #380: Modifies whitespace preservation in systemPromptSync.ts for leading/trailing newlines — addresses the same code-level whitespace handling concern.
• Fix all patches for CC 2.1.2 #352: Patch subsystem changes that consume showDiff and globalReplace utilities introduced in this PR.

Poem

🐰 A diff so fine, with colors bright,
Old in red, new in green light,
--show-unchanged tells the tale,
Of patches patched without fail,
Whitespace preserved, context clear—
Patching magic, hopping near! 🎨

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

• 📝 Generate docstrings

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