Using Git Worktrees

---
name: using-git-worktrees
description: Use when starting feature work that needs isolation from the current workspace, or before executing a non-trivial implementation plan that risks polluting the working tree. Creates an isolated git worktree with directory-selection priority and gitignore safety verification.
---

# Using Git Worktrees

## Overview

Git worktrees create isolated workspaces sharing the same repository, allowing work on multiple branches simultaneously without switching.

**Core principle:** Systematic directory selection + safety verification = reliable isolation.

**Announce at start:** "I'm using the using-git-worktrees skill to set up an isolated workspace."

## Directory Selection Process

Follow this priority order:

### 1. Check Existing Directories

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

**If found:** Use that directory. If both exist, `.worktrees` wins.

### 2. Check CLAUDE.md

```bash
grep -i "worktree.*director" CLAUDE.md 2>/dev/null
```

**If preference specified:** Use it without asking.

### 3. Ask User

If no directory exists and no CLAUDE.md preference:

```
No worktree directory found. Where should I create worktrees?

1. .worktrees/ (project-local, hidden)
2. ~/.claude/worktrees/<project-name>/ (global location)

Which would you prefer?
```

## Safety Verification

### For Project-Local Directories (.worktrees or worktrees)

**MUST verify directory is ignored before creating worktree:**

```bash
# Check if directory is ignored (respects local, global, and system gitignore)
git check-ignore -q .worktrees 2>/dev/null || git check-ignore -q worktrees 2>/dev/null
```

**If NOT ignored** (this means a real commit to the user's repo, so surface it and confirm before writing):

1. Show the exact `.gitignore` line you'd add and note that it needs a commit; ask before proceeding.
2. On confirmation: add the line to `.gitignore` and commit it.
3. Proceed with worktree creation.

**Why critical:** Prevents accidentally committing worktree contents to the repository.

### For Global Directory (~/.claude/worktrees)

No .gitignore verification needed - outside project entirely.

## Creation Steps

### 1. Detect Project Name

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

### 2. Create Worktree

```bash
# Determine full path
# Note: tilde is not expanded inside case patterns, so match the literal
# and expand $HOME explicitly in the path (a literal ~ in the path would not
# expand either — git worktree add would create a directory named "~").
case "$LOCATION" in
  .worktrees|worktrees)
    path="$LOCATION/$BRANCH_NAME"
    ;;
  "$HOME"/.claude/worktrees/*|~/.claude/worktrees/*)
    path="$HOME/.claude/worktrees/$project/$BRANCH_NAME"
    ;;
esac

# Create worktree with new branch
git worktree add "$path" -b "$BRANCH_NAME"
cd "$path"
```

**If `git worktree add` fails** because the branch or the path already exists, do not force it. Surface the conflict and offer two exits: resume work in the existing worktree/branch, or retry with a new suffixed name (`<branch>-2`, `<path>-2`). Picking silently risks attaching to someone else's in-flight work.

### 3. Run Project Setup

Auto-detect and run 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
```

### 4. Verify Clean Baseline

Run tests to ensure worktree starts clean:

```bash
# Examples - use project-appropriate command
npm test
cargo test
pytest
go test ./...
```

**If tests fail:** Report failures, ask whether to proceed or investigate.

**If tests pass:** Report ready.

### 5. Report Location

```
Worktree ready at <full-path>
Tests passing (<N> tests, 0 failures)
Ready to implement <feature-name>
```

## Quick Reference

| Situation | Action |
|-----------|--------|
| `.worktrees/` exists | Use it (verify ignored) |
| `worktrees/` exists | Use it (verify ignored) |
| Both exist | Use `.worktrees/` |
| Neither exists | Check CLAUDE.md → Ask user |
| Directory not ignored | Surface + confirm, then add to .gitignore + commit |
| Tests fail during baseline | Report failures + ask |
| No package.json/Cargo.toml | Skip dependency install |

## Common Mistakes

### Skipping ignore verification

- **Problem:** Worktree contents get tracked, pollute git status
- **Fix:** Always use `git check-ignore` before creating project-local worktree

### Assuming directory location

- **Problem:** Creates inconsistency, violates project conventions
- **Fix:** Follow priority: existing > CLAUDE.md > ask

### Proceeding with failing tests

- **Problem:** Can't distinguish new bugs from pre-existing issues
- **Fix:** Report failures, get explicit permission to proceed

### Hardcoding setup commands

- **Problem:** Breaks on projects using different tools
- **Fix:** Auto-detect from project files (package.json, etc.)

## Example Workflow

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

[Check .worktrees/ - exists]
[Verify ignored - git check-ignore confirms .worktrees/ is ignored]
[Create worktree: git worktree add .worktrees/auth -b feature/auth]
[Run npm install]
[Run npm test - 47 passing]

Worktree ready at /path/to/myproject/.worktrees/auth
Tests passing (47 tests, 0 failures)
Ready to implement auth feature
```

## Red Flags

**Never:**
- Add to or commit `.gitignore` without surfacing the change and confirming first
- Create worktree without verifying it's ignored (project-local)
- Skip baseline test verification
- Proceed with failing tests without asking
- Assume directory location when ambiguous
- Skip CLAUDE.md check

**Always:**
- Follow directory priority: existing > CLAUDE.md > ask
- Verify directory is ignored for project-local
- Auto-detect and run project setup
- Verify clean test baseline

## Integration

**Pairs with:**
- `/execute` — when an implementation plan touches enough files to risk polluting the working tree, set up a worktree first.
- Any task that needs an isolated workspace alongside in-flight work on `main`.
- `/orchestrate` — calls this skill once per concurrent unit it places in a worktree (Q2 placement).

**Deferred (v2) — N concurrent worktrees.** This skill is single-worktree by shape. An additive **N-worktree registry** is planned — `.claude/.worktrees-active.md` (gitignored): one row per active worktree (branch / path / owning-unit / file-scope claim), with a collision-claim check at creation and teardown + orphan-surfacing discipline. It does **not** change anything above — single-worktree behaviour is unchanged. See `orchestrate/DEFERRED-DESIGN.md` for the full design and its trigger.