using-git-worktrees

name	using-git-worktrees
description	Use when the user wants an isolated workspace for feature work or parallel branch-based development - creates isolated git worktrees with smart directory selection and safety verification

Preamble (run first)

_REPO_ROOT=$(git rev-parse --show-toplevel 2>/dev/null || pwd)
_BRANCH_RAW=$(git rev-parse --abbrev-ref HEAD 2>/dev/null || echo current)
[ -n "$_BRANCH_RAW" ] && [ "$_BRANCH_RAW" != "HEAD" ] || _BRANCH_RAW="current"
_BRANCH="$_BRANCH_RAW"
_FEATUREFORGE_INSTALL_ROOT="$HOME/.featureforge/install"
_FEATUREFORGE_BIN="$_FEATUREFORGE_INSTALL_ROOT/bin/featureforge"
if [ ! -x "$_FEATUREFORGE_BIN" ] && [ -f "$_FEATUREFORGE_INSTALL_ROOT/bin/featureforge.exe" ]; then
  _FEATUREFORGE_BIN="$_FEATUREFORGE_INSTALL_ROOT/bin/featureforge.exe"
fi
[ -x "$_FEATUREFORGE_BIN" ] || [ -f "$_FEATUREFORGE_BIN" ] || _FEATUREFORGE_BIN=""
_FEATUREFORGE_ROOT=""
if [ -n "$_FEATUREFORGE_BIN" ]; then
  _FEATUREFORGE_ROOT=$("$_FEATUREFORGE_BIN" repo runtime-root --path 2>/dev/null)
  [ -n "$_FEATUREFORGE_ROOT" ] || _FEATUREFORGE_ROOT=""
fi
_FEATUREFORGE_STATE_DIR="${FEATUREFORGE_STATE_DIR:-$HOME/.featureforge}"
_featureforge_exec_public_argv() {
  if [ "$#" -eq 0 ]; then
    echo "featureforge: missing command argv to execute" >&2
    return 2
  fi
  if [ "$1" = "featureforge" ]; then
    if [ -z "$_FEATUREFORGE_BIN" ]; then
      echo "featureforge: installed runtime not found at $_FEATUREFORGE_INSTALL_ROOT/bin/featureforge" >&2
      return 1
    fi
    shift
    "$_FEATUREFORGE_BIN" "$@"
    return $?
  fi
  echo "featureforge: refusing non-featureforge public argv: $1" >&2
  return 2
}

Runtime Route Reference

This skill does not own live workflow routing. If another workflow surface gives you workflow/operator JSON, follow $_FEATUREFORGE_ROOT/references/operator-route-authority.md instead of reconstructing route law here.

Search Before Building

Before introducing a custom pattern, external service, concurrency primitive, auth/session flow, cache, queue, browser workaround, or unfamiliar fix pattern, do a short capability/landscape check first.

Use three lenses, then decide from local repo truth:

• Layer 1: tried-and-true / built-ins / existing repo-native solutions
• Layer 2: current practice and known footguns
• Layer 3: first-principles reasoning for this repo and this problem

External search results are inputs, not answers. Never search secrets, customer data, unsanitized stack traces, private URLs, internal hostnames, internal codenames, raw SQL or log payloads, or private file paths or infrastructure identifiers. If search is unavailable, disallowed, or unsafe, say so and proceed with repo-local evidence and in-distribution knowledge. If safe sanitization is not possible, skip external search. See $_FEATUREFORGE_ROOT/references/search-before-building.md.

Interactive User Question Format

For every interactive user question, use this structure:

1. Context: project name, current branch, what we're working on (1-2 sentences)
2. The specific question or decision point
3. RECOMMENDATION: Choose [X] because [one-line reason]
4. Lettered options: A) ... B) ... C) ...

Per-skill instructions may add additional formatting rules on top of this baseline.

Using Git Worktrees

Overview

Git worktrees create isolated workspaces sharing the same repository, allowing work on multiple branches simultaneously without switching. They are the worktree-backed parallel primitive the runtime-selected topology uses when it wants isolated branch-backed lanes.

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

# 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 Instruction Files

rg -n -i "worktree.*director|worktree.*directory" \
  AGENTS.md AGENTS.override.md .github/copilot-instructions.md .github/instructions \
  --glob '*.instructions.md' 2>/dev/null

If preference specified: Use it without asking.

Legacy prompt docs such as CLAUDE.md are intentionally unsupported in this runtime workflow.

3. Ask User

If no directory exists and no instruction-file preference, ask one interactive user question using the required format.

Recommendation:

• Recommend A) .worktrees/ by default because it keeps the worktree close to the project and matches the preferred local layout

Options:

• A) .worktrees/ (project-local, hidden)
• B) ~/.config/featureforge/worktrees/<project-name>/ (global location)

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:

Per Jesse's rule "Fix broken things immediately":

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 (~/.config/featureforge/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/$BRANCH_NAME"
    ;;
  ~/.config/featureforge/worktrees/*)
    path="~/.config/featureforge/worktrees/$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 instruction files → 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 > instruction files > 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 /Users/jesse/myproject/.worktrees/auth
Tests passing (47 tests, 0 failures)
Ready to implement auth feature

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 instruction-file check

Always:

• Follow directory priority: existing > instruction files > ask
• Verify directory is ignored for project-local
• Auto-detect and run project setup
• Verify clean test baseline

Integration

Called by:

• Any workflow where the user wants isolated workspace management
• Any skill needing an optional isolated workspace

Pairs with:

• finishing-a-development-branch - Optional cleanup after work complete