Monorepo Package Extractor

What this skill does

Carves a single workspace package out of a pnpm or yarn monorepo into its own git repository, preserving the commit history that touched that package. The result is a fresh repo ready to push to a new origin.

Inputs

• monorepo_dir: absolute path to the source monorepo (must be a clean git tree).
• package_path: relative path of the package to extract (e.g., packages/parser).
• target_dir: empty directory where the new repo will be created.
• Requires git-filter-repo installed (pip install git-filter-repo or brew install git-filter-repo).

Steps

1. Verify monorepo_dir is clean: git -C <monorepo_dir> status --porcelain must be empty.
2. Confirm <monorepo_dir>/<package_path>/package.json exists; abort otherwise.
3. Clone the monorepo into target_dir: git clone --no-local <monorepo_dir> <target_dir>. The --no-local flag forces full object copy.
4. Inside target_dir run git filter-repo --path <package_path> --path-rename <package_path>/:. This rewrites history so only commits touching the package remain and the package becomes the repo root.
5. Reset remotes: git -C <target_dir> remote remove origin (filter-repo strips this anyway, but verify).
6. Read package.json in the extracted repo and remove workspace-protocol dependencies (workspace:*) — replace with the pinned version from the monorepo's lockfile (pnpm why <dep> or read pnpm-lock.yaml).
7. Copy a minimal .gitignore, LICENSE, and README.md if missing in the extracted repo.
8. Run git -C <target_dir> log --oneline | wc -l and record the surviving commit count.
9. Run npm install (or pnpm/yarn) inside the new repo to confirm the package builds standalone.

Output

A populated directory at target_dir containing the extracted repo with rewritten history. A summary printed to stdout listing surviving commit count, removed workspace:* deps, and any unresolved imports the package made into sibling packages.

Verification

Run git -C <target_dir> log --all --oneline -- <some-known-file> and compare against the same query in the monorepo (filtering by package_path); commit counts must match. Run the package's npm test (or pnpm test) inside the new repo — if it depends on a sibling, fail loudly with the missing import path. Diff the extracted package.json against the monorepo's to confirm only workspace:* rewrites changed.

Edge cases

• Package imports a sibling monorepo package: extraction will fail at install; report the missing peers and stop.
• Files that moved across package_path historically: git filter-repo --path-glob may need to run before the rename. Detect via git log --follow on a representative file.
• Monorepo with submodules: filter-repo strips them; re-add manually if needed.
• Empty target dir requirement: abort if target_dir exists and is non-empty rather than overwrite.