using-git-worktrees

Creates isolated git worktrees for parallel feature development without branch switching. Sets up clean, reproducible development environments with proper gitignore rules and dependency installation so that work on one feature never corrupts another. A core spellbook capability for managing concurrent development tracks.

Auto-invocation: Your coding assistant will automatically invoke this skill when it detects a matching trigger.

Use when starting feature work that needs isolation from current workspace, or setting up parallel development tracks. Triggers: 'worktree', 'separate branch', 'isolate this work', 'don't mess up current work', 'work on two things at once', 'parallel workstreams', 'new branch for this', 'keep my current work safe'.

Origin

This skill originated from obra/superpowers.

Workflow Diagram

Workspace isolation via git worktrees with safety verification, dependency setup, and clean test baseline enforcement.

flowchart TD
    Start([Start: Worktree Request]) --> CheckExisting{Existing Directory?}

    CheckExisting -->|.worktrees exists| UseWorktrees[Use .worktrees/]
    CheckExisting -->|worktrees exists| UseWorktreesAlt[Use worktrees/]
    CheckExisting -->|Both exist| UseWorktrees
    CheckExisting -->|Neither| CheckClaude{CLAUDE.md Preference?}

    CheckClaude -->|Yes| UsePref[Use Specified Path]
    CheckClaude -->|No| AskUser[Ask User for Location]

    AskUser --> LocationChoice{Project-Local or Global?}
    LocationChoice -->|Project-Local| UseWorktrees
    LocationChoice -->|Global| UseGlobal[Use ~/.local/spellbook/worktrees/]

    UseWorktrees --> SafetyCheck
    UseWorktreesAlt --> SafetyCheck
    UsePref --> PathType{Project-Local Path?}

    PathType -->|Yes| SafetyCheck
    PathType -->|No| CreateWorktree

    SafetyCheck{git check-ignore Passes?}
    SafetyCheck -->|Yes| CreateWorktree
    SafetyCheck -->|No| FixIgnore[Add to .gitignore]
    FixIgnore --> CommitIgnore[Commit .gitignore Change]
    CommitIgnore --> SafetyCheck

    UseGlobal --> CreateWorktree

    CreateWorktree[git worktree add] --> WorktreeExists{Worktree Already Exists?}
    WorktreeExists -->|Yes| ReportError[Report Error: Ask New Name]
    WorktreeExists -->|No| DetectProject[Detect Project Type]

    DetectProject --> SetupDeps{Setup Dependencies}
    SetupDeps -->|package.json| NpmInstall[npm install]
    SetupDeps -->|Cargo.toml| CargoBuild[cargo build]
    SetupDeps -->|requirements.txt| PipInstall[pip install]
    SetupDeps -->|pyproject.toml| UvSync[poetry install / uv sync]
    SetupDeps -->|go.mod| GoMod[go mod download]
    SetupDeps -->|None found| SkipDeps[Skip Dependency Install]

    NpmInstall --> SetupGate{Setup Succeeded?}
    CargoBuild --> SetupGate
    PipInstall --> SetupGate
    UvSync --> SetupGate
    GoMod --> SetupGate
    SkipDeps --> RunTests

    SetupGate -->|Yes| RunTests[Run Baseline Tests]
    SetupGate -->|No| ReportSetupFail[Report Failure: Ask User]

    RunTests --> TestGate{Tests Pass?}
    TestGate -->|Yes| ReportReady[Report Worktree Ready]
    TestGate -->|No| ReportTestFail[Report Failures: Ask User]

    ReportReady --> SelfCheck{Self-Check Passed?}
    SelfCheck -->|Yes| Done([Worktree Ready])
    SelfCheck -->|No| Resolve[STOP: Resolve Issues]

    style Start fill:#4CAF50,color:#fff
    style Done fill:#4CAF50,color:#fff
    style CheckExisting fill:#FF9800,color:#fff
    style CheckClaude fill:#FF9800,color:#fff
    style LocationChoice fill:#FF9800,color:#fff
    style PathType fill:#FF9800,color:#fff
    style SafetyCheck fill:#f44336,color:#fff
    style WorktreeExists fill:#FF9800,color:#fff
    style SetupDeps fill:#FF9800,color:#fff
    style SetupGate fill:#f44336,color:#fff
    style TestGate fill:#f44336,color:#fff
    style SelfCheck fill:#f44336,color:#fff
    style UseWorktrees fill:#2196F3,color:#fff
    style UseWorktreesAlt fill:#2196F3,color:#fff
    style UsePref fill:#2196F3,color:#fff
    style AskUser fill:#2196F3,color:#fff
    style UseGlobal fill:#2196F3,color:#fff
    style FixIgnore fill:#2196F3,color:#fff
    style CommitIgnore fill:#2196F3,color:#fff
    style CreateWorktree fill:#2196F3,color:#fff
    style ReportError fill:#2196F3,color:#fff
    style DetectProject fill:#2196F3,color:#fff
    style NpmInstall fill:#2196F3,color:#fff
    style CargoBuild fill:#2196F3,color:#fff
    style PipInstall fill:#2196F3,color:#fff
    style UvSync fill:#2196F3,color:#fff
    style GoMod fill:#2196F3,color:#fff
    style SkipDeps fill:#2196F3,color:#fff
    style RunTests fill:#2196F3,color:#fff
    style ReportReady fill:#2196F3,color:#fff
    style ReportSetupFail fill:#2196F3,color:#fff
    style ReportTestFail fill:#2196F3,color:#fff
    style Resolve fill:#f44336,color:#fff

Legend

Color	Meaning
Green (#4CAF50)	Skill invocation
Blue (#2196F3)	Command/action
Orange (#FF9800)	Decision point
Red (#f44336)	Quality gate

Cross-Reference

Node	Source Reference
Start: Worktree Request	Inputs: feature_name required (line 25)
Existing Directory?	Directory Selection Process step 1 (lines 43-51)
CLAUDE.md Preference?	Directory Selection Process step 2 (lines 53-59)
Ask User for Location	Directory Selection Process step 3 (lines 61-72)
git check-ignore Passes?	Safety Verification: verify directory is ignored (lines 76-95)
Add to .gitignore	Safety Verification: fix if not ignored (lines 97-100)
git worktree add	Creation Steps step 2 (lines 114-133)
Detect Project Type	Creation Steps step 3: auto-detect setup (lines 135-152)
Setup Dependencies	Creation Steps step 3: language-specific install (lines 140-152)
Run Baseline Tests	Creation Steps step 4: verify clean baseline (lines 156-178)
Tests Pass?	Reflection block: do tests pass in new worktree? (lines 168-174)
Report Worktree Ready	Creation Steps step 5: report location (lines 180-186)
Self-Check Passed?	Self-Check checklist (lines 296-304)

Skill Content

# Using Git Worktrees

<ROLE>
Build Engineer specializing in workspace isolation. Your reputation depends on clean, reproducible development environments that never corrupt the main workspace. Improper worktree setup causes repository corruption and lost work. This is very important.
</ROLE>

**Announce:** "Using git-worktrees skill for isolated workspace."

## Invariant Principles

1. **Directory precedence:** existing > CLAUDE.md > ask user (never assume)
2. **Safety gate:** Project-local worktrees MUST be gitignored before creation
3. **Clean baseline:** Tests must pass before implementation begins (interactive default; autonomous mode applies graduated policy — see Autonomous Mode)
4. **Auto-detect over hardcode:** Infer setup from manifest files

## Inputs

| Input | Required | Description |
|-------|----------|-------------|
| `feature_name` | Yes | Name for the worktree branch (e.g., "add-dark-mode") |
| `base_branch` | No | Branch to base worktree on (defaults to current HEAD) |
| `worktree_preference` | No | Explicit path preference from CLAUDE.md or user |

## Outputs

| Output | Type | Description |
|--------|------|-------------|
| `worktree_path` | Path | Absolute path to created worktree directory |
| `branch_name` | String | Name of the created branch |
| `baseline_status` | Report | Test results confirming clean starting state |

---

## Directory Selection Process

Follow this priority order:

### 1. Check Existing Directories

```bash
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. ~/.local/spellbook/worktrees/<project-name>/ (global location)

Which would you prefer?
```

## Safety Verification

<CRITICAL>
Worktree contents committed to the repository causes permanent pollution. This gate is non-negotiable: verify gitignore status before creating any project-local worktree.
</CRITICAL>

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

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

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

<analysis>
Before creating worktree:
- Does target directory already exist?
- Is directory preference established (existing > CLAUDE.md > ask)?
- Is project-local path gitignored?
If NOT ignored: add to .gitignore + commit immediately. Worktree contents must never be tracked.
</analysis>

**If NOT ignored:**
1. Add appropriate line to .gitignore
2. Commit the change
3. Proceed with worktree creation

### For Global Directory (~/.local/spellbook/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
case $LOCATION in
  .worktrees|worktrees)
    path="$LOCATION/$BRANCH_NAME"
    ;;
  ~/.local/spellbook/worktrees/*)
    path="~/.local/spellbook/worktrees/$project/$BRANCH_NAME"
    ;;
esac

# Check if branch/worktree already exists
git worktree list | grep -q "$BRANCH_NAME" && echo "ERROR: Worktree exists"

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

### 3. Run Project Setup

Auto-detect and run appropriate setup:

```bash
if [ -f package.json ]; then npm install; fi
if [ -f Cargo.toml ]; then cargo build; fi
if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
if [ -f pyproject.toml ]; then poetry install || uv sync; fi
if [ -f go.mod ]; then go mod download; fi
```

**If setup fails:** Report specific failure. Ask whether to proceed or troubleshoot.

### 4. Verify Clean Baseline

Run tests to ensure worktree starts clean:

```bash
# Use project-appropriate command: npm test / cargo test / pytest / go test ./...
```

<reflection>
After worktree creation:
- Did `git worktree add` succeed?
- Are dependencies installed?
- Do tests pass in new worktree?
IF NO to any: Report failure, do NOT proceed with implementation.
</reflection>

**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>
```

## Autonomous Mode Behavior

Check context for autonomous mode indicators:
- "Mode: AUTONOMOUS" or "autonomous mode"
- `worktree` preference specified (e.g., "single", "per_parallel_track", "none")

When autonomous mode is active:

### Skip These Interactions
- "Where should I create worktrees?" — use default (.worktrees/) or CLAUDE.md preference
- "Tests fail during baseline — ask whether to proceed" — proceed if minor, pause if critical

### Make These Decisions Autonomously
- Directory location: Use .worktrees/ as default if no existing directory or CLAUDE.md preference
- Gitignore fix: Always fix automatically (add to .gitignore + commit)
- Minor test failures: Log and proceed; major failures pause

### Circuit Breakers (Always Pause For)
- All tests failing (baseline completely broken)
- Git worktree command fails (structural git issue)
- .gitignore cannot be modified (permissions or other issue)

## 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 | Add to .gitignore + commit |
| Tests fail during baseline | Report failures + ask |
| Worktree already exists | Report error, ask for new name |
| Setup command fails | Report failure, ask how to proceed |
| No package.json/Cargo.toml | Skip dependency install |

## Common Mistakes

| Mistake | Problem | Fix |
|---------|---------|-----|
| Skip ignore verification | Worktree contents get tracked, pollute git status | Always `git check-ignore` before creating project-local worktree |
| Assume directory location | Creates inconsistency, violates project conventions | Follow priority: existing > CLAUDE.md > ask |
| Proceed with failing tests | Can't distinguish new bugs from pre-existing issues | Report failures, get explicit permission to proceed |
| Hardcode setup commands | Breaks on projects using different tools | Auto-detect from manifest files |

## Example Workflow

```
[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 /Users/jesse/myproject/.worktrees/auth
Tests passing (47 tests, 0 failures)
Ready to implement auth feature
```

<FORBIDDEN>
- Creating worktrees in unignored project-local directories
- Proceeding with implementation when baseline tests fail
- Assuming worktree location without checking precedence
- Modifying files in main workspace while in worktree context
- Leaving orphaned worktrees after feature completion
- Skipping safety verification for speed
</FORBIDDEN>

<CRITICAL>
## Self-Check

Before reporting worktree ready — if ANY unchecked, STOP and resolve:

- [ ] Directory location follows precedence (existing > CLAUDE.md > asked)
- [ ] Project-local path verified gitignored (or global path used)
- [ ] `git worktree add` completed successfully
- [ ] Dependencies installed for project type
- [ ] Baseline tests pass in new worktree
</CRITICAL>

## 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** — Work happens in this worktree (supports both batch and subagent modes)

<FINAL_EMPHASIS>
Worktree isolation protects the main workspace from experimental damage. Skipping safety verification causes repository pollution requiring manual cleanup. Proceeding without baseline tests makes it impossible to distinguish new bugs from pre-existing failures. Take the time to do it right.
</FINAL_EMPHASIS>