RemoteDiff

A native macOS app for viewing git diffs from remote servers over SSH, with side-by-side file comparison and live change watching. Includes a CLI tool for opening repos directly from the terminal.

Features

• Three view modes — Side-by-side full file, diff hunks, or single-pane full file (dual-pane modes scroll in sync)
• SSH git diff — Fetches diffs from remote hosts via /usr/bin/ssh, shell-agnostic (bash, fish, zsh)
• Live watching — ControlMaster-based persistent SSH with 2s polling and 800ms debounce
• Connection management — Save SSH connections with multiple repositories, auto-fetch on selection
• CLI launcher — Open repos from the terminal: remotediff host:path (like code for VS Code)
• Untracked & staged files — Option to include untracked and staged files in the diff
• Remote branch display — Shows the current branch on the remote, auto-refreshes
• 30+ language configs — File-extension-based language detection for syntax-aware rendering
• SSH config integration — Auto-parses ~/.ssh/config for host picker
• Diff result caching — Switch between repos without re-fetching
• Keyboard shortcuts — ⌘R refresh, ⌘[ ⌘] navigate files, ⌘↑ ⌘↓ jump between changes

Building

swift build
swift test       # 121 tests
open RemoteDiff.xcodeproj

Distributing

./scripts/build-app.sh

Creates .build/release/RemoteDiff.app and a .zip ready to share. On the target Mac, unzip and drag to /Applications. First launch: right-click → Open to bypass Gatekeeper (app is not notarized).

CLI Tool

Open remote repos directly from the terminal — similar to code for VS Code:

# Install the CLI (creates a symlink in /usr/local/bin)
./scripts/remotediff --install

# Basic usage
remotediff mac-studio:Development/myapp/api

# With SSH user (prompts for password if needed)
remotediff ernesto@mac-studio:Development/myapp/api

# With options
remotediff mac-studio:~/projects/api --ref main
remotediff prod-server:apps/backend --ref HEAD~3 --staged --untracked

The CLI automatically finds or creates a matching connection and repository in the app, then fetches the diff. If RemoteDiff is already running, it switches to the requested repo; otherwise it launches the app.

Password support: When SSH needs a password or key passphrase, a native macOS dialog appears automatically — no terminal interaction required. This works both from the CLI and from the GUI.

After building with build-app.sh, the CLI is also bundled inside the app at RemoteDiff.app/Contents/Resources/remotediff.

Usage

From the GUI

1. Click + to create a connection and enter an SSH host
2. Add repositories with a path and git ref
3. Select a repo — auto-fetches the diff and displays in side-by-side mode
4. Use the segmented picker to switch between Side by Side, Diff, and Full File views
5. Use ↑/↓ buttons (or ⌘↑/⌘↓) to jump between changes
6. Toggle Watch for live change detection

From the Terminal

remotediff [user@]<host>:<path> [--ref REF] [--staged] [--untracked]

Project Structure

RemoteDiff/
├── Models/
│   ├── DiffModels.swift          # DiffLine, DiffHunk, FileDiff, SSHHost, RepoSelection
│   ├── DiffParser.swift          # Unified diff parser
│   ├── DisplayLineBuilder.swift  # Builds display lines for all view modes
│   ├── SSHConfig.swift           # ~/.ssh/config parser
│   ├── ConnectionStore.swift     # Connection + Repository persistence
│   └── DeepLink.swift            # URL scheme parser for CLI integration
├── Services/
│   ├── SSHService.swift          # SSH execution, diff fetching, caching
│   ├── FileContentService.swift  # Full file content fetching for side-by-side
│   └── ControlMasterWatcher.swift # Persistent SSH + change polling
├── Views/
│   ├── CodePaneView.swift        # Unified code rendering component
│   ├── DiffView.swift            # View mode switching + file header
│   ├── SidebarView.swift         # Connection/repo browser + file list
│   ├── LiveStatusBar.swift       # Watcher status indicator
│   └── LanguageConfig.swift      # 30+ language definitions
├── ContentView.swift             # Main NavigationSplitView
└── RemoteDiffApp.swift           # App entry point + URL scheme handler
scripts/
├── build-app.sh                  # Builds .app bundle + .zip
├── remotediff                    # CLI launcher script
└── remotediff-askpass            # SSH_ASKPASS helper (native macOS password dialog)

Requirements

• macOS 13 Ventura or later
• SSH access to remote hosts (key-based auth recommended; password auth supported via native dialog)
• Git installed on the remote server