GitHub - chalmagean/diffreview

A native macOS tool for reviewing local code changes GitHub-PR style, built to send that review back to Claude Code (or anything else that reads markdown).

Run diffreview in a git repository and a window opens with the diff. Leave inline comments on lines or ranges, file-level comments and an overall summary, then click Submit review. The review is printed to stdout as markdown and the process exits.

Requirements

macOS 14 or later
Swift 6 toolchain (Xcode or the Command Line Tools)
git on your PATH

Install

git clone <this repo> diffreview && cd diffreview
swift build -c release
install -m 755 .build/release/diffreview ~/.local/bin/diffreview   # or any directory on your PATH

Updating

After pulling or changing the code, rebuild and reinstall from the repo:

swift build -c release
install -m 755 .build/release/diffreview ~/.local/bin/diffreview   # same directory as before

diffreview → About diffreview shows the version and when the running binary was built, so you can tell whether you're on the latest build.

Usage

diffreview                 # uncommitted changes: `git diff HEAD` plus untracked files
diffreview --base main     # commits on the current branch since its merge-base with main
diffreview --help

Result	stdout	exit code
Submit review	the review as markdown	0
Close window / quit without submitting	nothing	1
No changes to review	nothing (message on stderr)	1
Not a git repository, unknown ref, bad arguments	nothing (message on stderr)	2

--base compares committed work only (merge-base..HEAD), like a pull request. Uncommitted changes are not included in that mode.

Reviewing

Click a line to comment on it. Shift-click another line in the same file to extend the comment to a range.
Drag across code to comment on just part of it: a few characters, or from the middle of one line to the middle of another.
⌘↩ adds the comment, Esc cancels. Existing comments can be edited or deleted.
Comment on file (in each file header) adds a file-level comment.
Finish review (⌘⇧↩) opens the summary box and the Submit review button.
Files can be collapsed. Files with more than 1,500 changed lines start collapsed.
Settings… (⌘,) picks the code font (any installed monospaced family, or the system SF Mono) and its size. The choice is remembered.

Drafts are saved automatically to .git/diffreview/comments.json, so closing the window doesn't lose work: the next run picks up where you left off. The file is deleted when you submit. If you close the window while a comment is still being typed, that text is kept as a comment.

Output format

# Code Review

Overall summary.

## path/to/file.swift

A file-level comment.

### Lines 42-45 (new)

```swift
let the = "selected lines"
```

The comment.

When only part of the lines was selected, the full lines are still shown for context, followed by a Selected text: block with the exact selection.

Line numbers refer to the new version of the file, or to the old version ((old)) when only deleted lines are selected. Selections that mix added and removed lines are shown as a diff block.

Claude Code integration

The repo ships a /diffreview command in .claude/commands/diffreview.md. Install it for all your projects:

mkdir -p ~/.claude/commands
cp .claude/commands/diffreview.md ~/.claude/commands/

It contains:

---
description: Open diffreview to review changes GitHub-style, then address the comments
argument-hint: [--base <ref>]
allowed-tools: Bash(diffreview) Bash(diffreview *)
---
!`diffreview $ARGUMENTS`
Address each review comment above. If something is unclear, ask before changing it.

Then run /diffreview (or /diffreview --base main) in any repository. Cancelling the review makes the command abort, so nothing is sent to Claude.

Timeout: Claude Code runs ! commands under the Bash tool's default timeout of 2 minutes, and reviews usually take longer. Raise it in ~/.claude/settings.json:

{
  "env": {
    "BASH_DEFAULT_TIMEOUT_MS": "3600000",
    "BASH_MAX_TIMEOUT_MS": "3600000"
  }
}

This also changes the default timeout for every other Bash command Claude Code runs.

Development

swift build
scripts/test.sh

Use scripts/test.sh rather than swift test. With only the Command Line Tools installed (no Xcode), swift test builds the swift-testing tests but runs none of them and still reports success. The script detects that setup and runs the tests through a small runner (scripts/TestRunner.swift). Under Xcode it just calls swift test.

Layout

Sources/DiffReviewCore: no UI. Runs git, parses unified diffs (renames, copies, binary files, mode changes, quoted paths, "\ No newline at end of file"), models comments, renders the markdown review and stores drafts.
Sources/diffreview: the AppKit/SwiftUI app.
Tests/DiffReviewCoreTests: parser and renderer tests, plus integration tests that run real git in temporary repositories.

Syntax highlighting isn't implemented yet. Sources/diffreview/SyntaxHighlighter.swift is the place to add it: each line is passed through SyntaxHighlighter.highlight(_:language:).

License

MIT