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difit is a CLI tool that lets you view and review local git diffs with a GitHub-style viewer. In addition to clean visuals, comments can be copied as prompts for AI. The local code review tool for the AI era!

⚡ Quick Start

Try it first

npx difit  # View the latest commit diff in WebUI

Install and use

npm install -g difit
difit  # View the latest commit diff in WebUI

Enable use from AI agents

npx skills add yoshiko-pg/difit # Add the Skill to your agent

🚀 Usage

Basic Usage

difit <target>                    # View single commit diff
difit <target> [compare-with]     # Compare two commits/branches

Single commit review

difit          # HEAD (latest) commit
difit 6f4a9b7  # Specific commit
difit feature  # Latest commit on feature branch

Compare two commits

difit @ main         # Compare with main branch (@ is alias for HEAD)
difit feature main   # Compare branches
difit . origin/main  # Compare working directory with remote main

Special Arguments

difit supports special keywords for common diff scenarios:

difit .        # All uncommitted changes (staging area + unstaged)
difit staged   # Staging area changes
difit working  # Unstaged changes only

GitHub PR

difit --pr https://github.com/owner/repo/pull/123

--pr mode fetches patches by running gh pr diff --patch under the hood.

Authentication is handled by GitHub CLI:

1. Login once (recommended): gh auth login
2. Token-based auth (CI/non-interactive): set GH_TOKEN or GITHUB_TOKEN

GitHub Enterprise Server

For Enterprise Server PRs, authenticate GitHub CLI against your Enterprise host:

1. gh auth login --hostname YOUR-ENTERPRISE-SERVER
2. Or set GH_HOST=YOUR-ENTERPRISE-SERVER with GH_TOKEN/GITHUB_TOKEN

Stdin

By using a pipe to pass unified diffs via stdin, you can view diffs from any tool with difit.

# View diffs from other tools
diff -u file1.txt file2.txt | difit

# Review saved patches
cat changes.patch | difit

# Compare against merge base
git diff --merge-base main feature | difit

# Review an entire existing file as newly added
git diff -- /dev/null path/to/file | difit

# Explicit stdin mode
git diff --cached | difit -

Stdin mode is selected with intent-first rules:

• - explicitly enables stdin mode
• If positional arguments (<target> / [compare-with]), --pr, or --tui are provided, difit treats the command as Git/PR/TUI mode and does not auto-read stdin
• Auto stdin detection applies only when no explicit mode is selected and stdin is a pipe/file/socket

⚙️ CLI Options

Flag	Default	Description
<target>	HEAD	Commit hash, tag, HEAD~n, branch, or special arguments
[compare-with]	-	Optional second commit to compare with (shows diff between the two)
--pr <url>	-	GitHub PR URL to review (e.g., https://github.com/owner/repo/pull/123)
--port	4966	Preferred port; falls back to +1 if occupied
--host	127.0.0.1	Host address to bind server to (use 0.0.0.0 for external access)
--no-open	false	Don't automatically open browser
--mode	split	Display mode: unified or split
--tui	false	Use terminal UI mode instead of WebUI
--clean	false	Clear all existing comments and viewed files on startup
--include-untracked	false	Automatically include untracked files in diff (only with . or working)
--keep-alive	false	Keep server running after browser disconnects (stop manually with Ctrl+C)

💬 Comment System

difit includes a review comment system that makes it easy to provide feedback to AI coding agents:

1. Add Comments: Click the comment button on any diff line or drag to select a range
2. Edit Comments: Edit existing comments with the edit button
3. Generate Prompts: Comments include a "Copy Prompt" button that formats the context for AI coding agents
4. Copy All: Use "Copy All Prompt" to copy all comments in a structured format
5. Persistent Storage: Comments are saved in browser localStorage per commit

Comment Prompt Format

src/components/Button.tsx:L42   # This line is automatically added
Make this variable name more descriptive

For range selections:

src/components/Button.tsx:L42-L48   # This line is automatically added
This section is unnecessary

🤖 Calling from Agents

You can install the following Skill to request reviews from users with difit.

npx skills add yoshiko-pg/difit

After an agent edits code, it will start the difit server.

🎨 Syntax Highlighting Languages

• JavaScript/TypeScript: .js, .jsx, .ts, .tsx
• Web Technologies: HTML, CSS, JSON, XML, Markdown
• Shell Scripts: .sh, .bash, .zsh, .fish
• Backend Languages: PHP, SQL, Ruby, Java, Scala, Perl
• Systems Languages: C, C++, C#, Rust, Go
• Mobile Languages: Swift, Kotlin, Dart
• Infrastructure as Code: Terraform (HCL)
• Others: Python, Protobuf, YAML, Solidity, Vim script

🔍 Auto-collapsed Files

difit automatically identifies and collapses certain files to keep your view clean:

• Deleted files: Removed files are auto-collapsed since they don't require close review
• Generated files: Auto-generated code is collapsed by default. This includes:
  • Lock files (package-lock.json, go.mod, Cargo.lock, Gemfile.lock, etc.)
  • Minified files (*.min.js, *.min.css)
  • Source maps (*.map)
  • Generated code:
    • Orval (*.msw.ts, *.zod.ts, *.api.ts)
    • Dart (*.g.dart, *.freezed.dart)
    • C# (*.g.cs, *.designer.cs)
    • Protobuf (*.pb.go, *.pb.cc, *.pb.h)
  • Frameworks:
    • Ruby on Rails (db/schema.rb)
    • Laravel (_ide_helper.php)
    • Gradle (gradle.lockfile)
    • Python (uv.lock, pdm.lock)
  • Generic generated files (*.generated.cs, *.generated.ts, *.generated.js)
  • Content-based detection:
    • Files containing @generated marker
    • Files containing DO NOT EDIT header
    • Language-specific generated headers (Go, Python, etc.)

🛠️ Development

# Install dependencies
pnpm install

# Start development server (with hot reload)
# This runs both Vite dev server and CLI with NODE_ENV=development
pnpm run dev

# Build and start production server
pnpm run start <target>

# Build for production
pnpm run build

# Run tests
pnpm test

# Run typecheck, lint, and format
pnpm run check
pnpm run format

Development Workflow

• pnpm run dev: Starts both Vite dev server (with hot reload) and CLI server simultaneously
• pnpm run start <target>: Builds everything and starts production server (for testing final build)
• Development mode: Uses Vite's dev server for hot reload and fast development
• Production mode: Serves built static files (used by npx and production builds)

🏗️ Architecture

• CLI: Commander.js for argument parsing with comprehensive validation
• Backend: Express server with simple-git for diff processing
• GitHub Integration: GitHub CLI (gh pr diff --patch) for PR patch retrieval
• Frontend: React 18 + TypeScript + Vite
• Styling: Tailwind CSS v4 with GitHub-like dark theme
• Syntax Highlighting: Prism.js with dynamic language loading
• Testing: Vitest for unit tests with co-located test files
• Quality: oxlint, oxfmt, lefthook pre-commit hooks

📋 Requirements

• Node.js ≥ 21.0.0
• Git repository with commits to review
• GitHub CLI (gh) for --pr mode

📄 License

MIT