feat(git): add git-delta for enhanced diff viewing

[HagaSpa]

Background / 背景

Add git-delta to enhance the readability of git diff and git log outputs with syntax highlighting and side-by-side view.
git diff や git log の出力を見やすくするため、シンタックスハイライトと横並び表示機能を持つ git-delta を追加します。

Changes / 変更内容

• Added git-delta to Brewfile for installation management

• Configured .gitconfig to use delta as the default pager

• Enabled side-by-side view mode for better diff comparison

• インストール管理のため Brewfile に git-delta を追加

• .gitconfig でデフォルトの pager として delta を設定

• より見やすい diff 比較のため横並び表示モードを有効化

Impact scope / 影響範囲

• Changes how git diff, git log, and other git commands display their output

• Only affects local git command output display

• No impact on git functionality or remote repositories

• git diff、git log、その他の git コマンドの出力表示方法を変更

• ローカルの git コマンド出力表示のみに影響

• git の機能やリモートリポジトリへの影響なし

Testing / 動作確認

• Verified git-delta is in Brewfile / Brewfile に git-delta が追加されていることを確認
• Confirmed git-delta is already installed / git-delta が既にインストール済みであることを確認
• Verified delta command works (version 0.18.2) / delta コマンドが動作することを確認（バージョン 0.18.2）
• Confirmed .gitconfig pager is set to delta / .gitconfig の pager が delta に設定されていることを確認

🤖 Generated with Claude Code

[claude]

Claude finished @HagaSpa's task —— View job

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PR Review: git-delta Integration

Todo List:

• Read repository guidelines (CLAUDE.md)
• Examine changed files (.gitconfig and Brewfile)
• Analyze code quality and best practices
• Check for potential bugs or issues
• Review performance considerations
• Assess security concerns
• Evaluate test coverage

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🔍 Code Review Summary

Overall Assessment: ✅ LGTM - Clean, well-tested implementation

This PR cleanly integrates git-delta for enhanced diff viewing. The changes are minimal, focused, and follow repository conventions perfectly.

📋 Detailed Analysis

✅ Code Quality & Best Practices

• Excellent: Changes follow the repository's declarative configuration approach
• Consistent: Brewfile entry follows existing package declaration patterns (brew "git-delta")
• Clean: .gitconfig changes are minimal and focused - only replacing less -R with delta
• Well-structured: Delta configuration is properly isolated in its own [delta] section
• Standards compliant: Git configuration follows standard gitconfig format

✅ Potential Bugs or Issues

• No issues found: The implementation is solid
• Backwards compatibility: If git-delta isn't installed, git will fall back gracefully to system pager
• Configuration safety: side-by-side = true is a safe, cosmetic setting with no functional risks
• Dependency management: Proper inclusion in Brewfile ensures git-delta is installed via the standard ./install.sh workflow

✅ Performance Considerations

• Positive impact: git-delta is generally faster than less -R for syntax highlighting
• Memory efficient: Delta uses efficient algorithms for diff processing
• No regression risk: Side-by-side view only affects display, not git operations
• Lazy loading: Delta only activates when git output is piped through it

✅ Security Concerns

• No security risks: git-delta is a well-established, trusted tool from the Rust ecosystem
• Minimal attack surface: Only affects local git output display
• No network operations: Delta is purely a local formatting tool
• Safe configuration: The side-by-side setting is purely cosmetic

✅ Test Coverage

• Manual testing completed: PR description shows thorough testing checklist
• Installation verified: Author confirmed git-delta v0.18.2 is working
• Configuration validated: Confirmed .gitconfig pager setting is correct
• Integration tested: Delta command functionality verified
• Appropriate for dotfiles: Manual testing is the standard approach for configuration changes

🎯 Specific Code Comments

.gitconfig:8 - Clean replacement of pager = less -R with pager = delta

• ✅ Maintains the same functionality while adding syntax highlighting
• ✅ Good choice to remove the redundant blank line at the end

.gitconfig:14-15 - Addition of [delta] section with side-by-side = true

• ✅ Proper isolation of delta-specific configuration
• ✅ Side-by-side mode enhances diff readability, especially for larger changes

Brewfile:10 - Addition of brew "git-delta"

• ✅ Correctly placed alphabetically within the brew packages section
• ✅ Follows the existing pattern used by other tools in the file

🔄 Repository Integration

• ✅ Follows CLAUDE.md guidelines: Adheres to the modular configuration approach
• ✅ Symbolic linking: .gitconfig is properly included in link.sh mapping (line 21)
• ✅ Installation workflow: Will be installed via existing ./install.sh script
• ✅ Consistent with repo philosophy: Adds another modern CLI tool to the curated collection

📝 Minor Suggestions (Optional)

1. Documentation: Consider adding git-delta to the "Development Tools Included" section in CLAUDE.md for future reference
2. Additional delta options: You might explore other delta features like line-numbers = true or navigate = true in future iterations

✅ Final Verdict

This is a high-quality, low-risk improvement that enhances the development experience without any functional downsides. The implementation is clean, well-tested, and follows all repository conventions.

Ready to merge! 🚀