Using Git Worktrees

---
name: using-git-worktrees
description: >
  Use before implementation when work should be isolated from the current
  branch. Triggers on: "use a worktree", "isolate this work",
  "don't touch main", experimental or risky changes that need isolation.
---

# Using Git Worktrees

Create an isolated branch workspace with safe defaults.

## Required Start

Announce: `I'm using the using-git-worktrees skill to set up an isolated workspace.`

## Directory Selection Priority

Check in order:

```bash
ls -d .worktrees 2>/dev/null     # Preferred (hidden)
ls -d worktrees 2>/dev/null      # Alternative
```

1. If `.worktrees/` exists — use it. If both exist, `.worktrees/` wins.
2. If `worktrees/` exists — use it.
3. Check project guidance file (e.g. `CLAUDE.md`) for a stated preference:
   ```bash
   grep -i "worktree.*director" CLAUDE.md 2>/dev/null
   ```
4. Ask user.

## Safety Check

For project-local worktree directories, verify ignore rules before creating:

```bash
git check-ignore -q .worktrees 2>/dev/null || git check-ignore -q worktrees 2>/dev/null
```

If **not** ignored:
1. Add the appropriate line to `.gitignore`.
2. **Commit the `.gitignore` change immediately** before proceeding — an uncommitted ignore entry is easy to lose and leaves the worktree contents exposed to accidental staging.

## Creation Steps

### 1. Detect project root and branch name

```bash
project=$(basename "$(git rev-parse --show-toplevel)")
```

Choose a descriptive `BRANCH_NAME` for the feature being isolated.

### 2. Create worktree and branch

```bash
git worktree add <path> -b <BRANCH_NAME>
```

**Critical:** The `cd <path>` in this step does not persist across separate shell calls. Use the full worktree path — `cd <path> && <command>` — in every subsequent Bash call rather than assuming the working directory carried over.

### 3. Run project setup

Auto-detect the project ecosystem and run the appropriate setup:

```bash
# Node.js
if [ -f package.json ]; then npm install; fi

# Rust
if [ -f Cargo.toml ]; then cargo build; fi

# Python
if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
if [ -f pyproject.toml ]; then poetry install; fi

# Go
if [ -f go.mod ]; then go mod download; fi
```

If none of these files exist, skip dependency installation and note it in the output.

### 4. Run baseline tests

Run the project-appropriate test command to confirm the worktree starts clean:

```bash
# Use whichever applies
npm test
cargo test
pytest
go test ./...
```

## Failure Handling

If baseline tests fail, report the failures and ask whether to continue or investigate before proceeding.

## Success Output

Report:
- Worktree path (full absolute path)
- Branch name
- Ecosystem detected and setup command(s) run
- Baseline test status (passing count or failure summary)

## Integration

Use with:
- `writing-plans`
- `subagent-driven-development` — REQUIRED before executing any tasks
- `executing-plans` — REQUIRED before executing any tasks

Cleanup is handled by `finishing-a-development-branch`.