using-git-worktrees

name	using-git-worktrees
description	Use when starting feature work that needs isolation from current workspace or before executing implementation plans - creates isolated git worktrees with smart directory selection and 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."

Proactive Setup

Before first use, ensure .worktrees/ is in the project's .gitignore:

# Add to the repo-root .gitignore if not already present
git_root="$(git rev-parse --show-toplevel)"
gitignore_path="$git_root/.gitignore"

grep -qxF '.worktrees' "$gitignore_path" 2>/dev/null \
  || grep -qxF '.worktrees/' "$gitignore_path" 2>/dev/null \
  || echo '.worktrees/' >> "$gitignore_path"

This prevents worktree contents from ever being tracked. Do this once per project rather than relying on runtime detection.

Directory Selection Process

Follow this priority order:

1. Check Existing Directories

# 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 Project Configuration

# Check common config files for worktree directory preference
grep -i "worktree.*director" CLAUDE.md AGENTS.md .github/copilot-instructions.md 2>/dev/null

If preference specified: Use it without asking.

3. Ask User

If no directory exists and no project configuration preference:

No worktree directory found. Where should I create worktrees?

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

Which would you prefer?

Safety Verification

For Project-Local Directories (.worktrees or worktrees)

MUST verify directory is ignored before creating worktree:

# 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:

Fix immediately before proceeding:

1. Add appropriate line to .gitignore
2. Commit the change
3. Proceed with worktree creation

Why critical: Prevents accidentally committing worktree contents to repository.

For Global Directory (~/.worktrees)

No .gitignore verification needed - outside project entirely.

Creation Steps

1. Detect Project Name

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

2. Create Worktree

# Determine full path
case $LOCATION in
  .worktrees|worktrees)
    path="$LOCATION/$BRANCH_NAME"
    ;;
  ~/.worktrees/*)
    path="~/.worktrees/$project/$BRANCH_NAME"
    ;;
esac

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

3. Run Project Setup

Auto-detect and run appropriate setup:

# 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:

# 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 project config → Ask user
Directory not ignored	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 > project config > 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 /home/user/myproject/.worktrees/auth
Tests passing (47 tests, 0 failures)
Ready to implement auth feature

Cleanup After Merge

Once work is completed and merged into the parent branch, always remove the worktree to avoid stale checkouts and disk bloat.

1. Verify the branch was merged

# Detect the default branch
base=$(git symbolic-ref refs/remotes/origin/HEAD 2>/dev/null | sed 's@^refs/remotes/origin/@@')
base=${base:-main}  # fallback to main if detection fails

# From the main working tree, confirm the feature branch is merged
git branch --merged "$base" | grep <feature-branch>

2. Remove the worktree

# Remove the worktree directory and its administrative files
git worktree remove <worktree-path>

If the worktree has uncommitted changes, Git will refuse. Use --force only after confirming nothing valuable remains:

git worktree remove --force <worktree-path>

3. Delete the feature branch

# Safe delete (fails if not merged)
git branch -d <feature-branch>

# Also remove the remote tracking branch if pushed
git push origin --delete <feature-branch>

4. Verify cleanup

# Confirm no stale worktrees remain
git worktree list

# Prune any worktrees whose directories were manually deleted
git worktree prune

Tip: Run git worktree list periodically to catch forgotten worktrees. Stale entries from manually deleted directories can be cleaned up with git worktree prune.

Red Flags

Never:

• 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 project configuration check
• Leave worktrees around after the branch has been merged

Always:

• Follow directory priority: existing > project config > ask
• Verify directory is ignored for project-local
• Auto-detect and run project setup
• Clean up worktrees and branches after merge
• Verify clean test baseline

Integration

Called by:

• brainstorming (Phase 4) - REQUIRED when design is approved and implementation follows
• Any skill needing isolated workspace

Pairs with:

• finishing-a-development-branch - REQUIRED for cleanup after work complete
• executing-plans or subagent-driven-development - Work happens in this worktree