# Comments (https://diffhub.blode.md/features/comments)

Leave review notes on any line and copy them as a prompt for an agent or teammate.

## Adding comments

Click any line in the diff to open the comment input. Type your note and press Enter to save it.

## Comment tags

| Tag            | Purpose                              |
| -------------- | ------------------------------------ |
| `[must-fix]`   | Critical issue that must be resolved |
| `[suggestion]` | Improvement suggestion               |
| `[nit]`        | Minor style or formatting note       |
| `[question]`   | Question about the code              |

## Copy as prompt

Click the copy button in the status bar to copy all comments as a formatted markdown prompt. This is useful when you want to hand review feedback to an agent or share it with a teammate.

## Storage

Comments are stored in `.git/diffhub-comments.json` inside the target repository. The file is gitignored by default and stays there between sessions.

# Diff Views (https://diffhub.blode.md/features/diff-views)

See your whole branch against the base branch or switch to uncommitted-only changes.

## Split vs unified

Toggle between split and unified views with the `s` key or the layout toggle in the status bar.

- **Split** - side-by-side view with the old file on the left and the new file on the right
- **Unified** - one stream of additions and deletions inline

## Diff modes

DiffHub supports two review modes from the status bar:

- **All** (default) - shows everything your branch changed since it diverged from the base branch. This is the mode most people want before push.
- **Uncommitted** - shows only your staged and unstaged changes against `HEAD`.

## Merge-base diffing

DiffHub diffs against `git merge-base HEAD <base-branch>`.

That means commits pushed to the base branch after you branched do not show up in the review. You only see what your branch changed.

# Introduction (https://diffhub.blode.md/)

Review your branch in cmux or a browser.

DiffHub is a local diff viewer for cmux.

It opens your branch in a browser split and compares it with the detected base branch, usually `origin/main`. If you do not use cmux, you can open the same view in a normal browser window.

[Watch the demo (2 min)](https://www.loom.com/share/e0203dd97b354508a791ecd339094a02)

## Quick start

```bash
npx diffhub@latest cmux
```

That starts DiffHub and opens your branch diff in a cmux browser split.

```bash
npx diffhub@latest
```

Use that if you want a normal browser tab instead.

### Global install

```bash
npm install -g diffhub
```

## What you get

- **Branch diff against the right base branch**. DiffHub uses the merge-base, so you see what your branch changed.
- **Split and unified views**. Toggle with `s`.
- **Inline comments**. Tag notes as `[must-fix]`, `[suggestion]`, `[nit]`, or `[question]`.
- **File sidebar**. Filter files with `/` and scan per-file `+` and `-` stats.
- **Auto-refresh while you work**. Keep the view open and see updates as files change.
- **Open in your tools**. Right-click to jump into Zed, VS Code, Terminal, or Finder.

Requires Node.js 20.11 or later and a git repository with at least one commit. cmux mode expects `cmux.app` on macOS at `/Applications/cmux.app`.

## Next steps

- [Usage](https://diffhub.blode.md/usage) - run DiffHub in cmux or a browser
- [Diff Views](https://diffhub.blode.md/features/diff-views) - review your whole branch or only uncommitted changes
- [Comments](https://diffhub.blode.md/features/comments) - leave review notes

# Usage (https://diffhub.blode.md/usage)

Run DiffHub in cmux or a browser and choose a base branch.

## cmux

```bash
npx diffhub@latest cmux
```

Run that inside any git repository. DiffHub starts the local viewer and opens it in a cmux browser split.

cmux mode currently expects `cmux.app` on macOS at `/Applications/cmux.app`.

Use these flags when you need them:

```bash
# Use a different base branch
diffhub cmux --base develop

# Point at a repo in another directory
diffhub cmux --repo ~/projects/my-app
```

## Browser

```bash
npx diffhub@latest
```

That starts the same viewer in your default browser.

## Commands

| Command | Description                              |
| ------- | ---------------------------------------- |
| `serve` | Start DiffHub in a normal browser window |
| `cmux`  | Start DiffHub in a cmux browser split    |

## `serve` options

| Flag                  | Default | Description                 |
| --------------------- | ------- | --------------------------- |
| `-p, --port <port>`   | `2047`  | Port to serve on            |
| `-r, --repo <path>`   | `cwd`   | Path to the git repository  |
| `-b, --base <branch>` | auto    | Base branch to diff against |
| `--no-open`           | —       | Skip automatic browser open |

## `cmux` options

| Flag                  | Default | Description                 |
| --------------------- | ------- | --------------------------- |
| `-r, --repo <path>`   | `cwd`   | Path to the git repository  |
| `-b, --base <branch>` | auto    | Base branch to diff against |

## Examples

```bash
# Open in cmux
diffhub cmux

# Use a different base branch in cmux
diffhub cmux --base develop

# Point cmux mode at a repo in another directory
diffhub cmux --repo ~/projects/my-app

# Use a different port in browser mode
diffhub --port 3000

# Don't open the browser automatically
diffhub --no-open
```

## Base branch detection

DiffHub auto-detects the base branch in this priority order:

1. `origin/main`
2. `origin/master`
3. `origin/develop`
4. `origin/dev`
5. Local `main`, `master`, `develop`, `dev`

Override with `--base <branch>` or the `DIFFHUB_BASE` environment variable if your repo uses a different naming convention.

## Keyboard shortcuts

| Key        | Action                         |
| ---------- | ------------------------------ |
| `j`        | Next file                      |
| `k`        | Previous file                  |
| `s`        | Toggle split / unified view    |
| `/` or `t` | Focus file filter              |
| `r`        | Force refresh diff             |
| `c`        | Collapse / expand current file |
| `Shift+C`  | Collapse all files             |
| `Shift+E`  | Expand all files               |

## Environment variables

| Variable                | Description                                     |
| ----------------------- | ----------------------------------------------- |
| `DIFFHUB_REPO`          | Path to the git repository (overrides cwd)      |
| `DIFFHUB_BASE`          | Base branch override (overrides auto-detection) |
| `DIFFHUB_DEBUG`         | Set to `1` for verbose git command logging      |
| `DIFFHUB_DISABLE_WATCH` | Set to `1` to disable file system watching      |