git-fast-worktree

A macOS tool that creates git worktrees using APFS copy-on-write cloning instead of git checkout. For large monorepos this can be orders of magnitude faster than git worktree add.

Install

go install github.com/orf/git-fast-worktree@latest

Usage

Run from within a git repository:

# Create a worktree at the given path
git fast-worktree add /tmp/my-worktree

# Create a worktree on a new branch
git fast-worktree add -b my-branch /tmp/my-worktree

# Create a worktree at a specific commit
git fast-worktree add /tmp/my-worktree origin/main

The CLI mirrors git worktree add flags:

$ git-fast-worktree add --help
Create a worktree using APFS clonefile

Usage:
  git-fast-worktree add [flags] <path> [<commit-ish>]

Flags:
  -b, --branch string         create a new branch
  -B, --force-branch string   create or reset a branch
  -h, --help                  help for add
      --no-track              do not set up tracking mode

How it works

1. git worktree add --no-checkout registers the worktree with git
2. Each top-level entry in the source repo (excluding .git) is cloned into the worktree using the APFS clonefile syscall, which recursively clones entire directory trees without copying data
3. git reset --no-refresh populates the git index to match HEAD

Because clonefile is copy-on-write, the worktree initially shares all data blocks with the source repo and only allocates new storage when files are modified.

Limitations

• macOS only - relies on the APFS clonefile syscall
• Same volume only - source and destination must be on the same APFS volume
• Copies the working tree as-is, including untracked and ignored files from the source