Agent Skills: Worktree Setup

Worktree Setup

Create an isolated git worktree with a feature branch for PACT workflows. This provides filesystem isolation so multiple features or sub-scopes can run in parallel without interference.

When to Use

• Starting a new feature workflow (/PACT:orchestrate, /PACT:comPACT)
• ATOMIZE phase creating sub-scope isolation
• Manually isolating work for a feature branch

Process

Follow these steps in order. Stop and report any errors to the user.

Step 1: Check for Existing Worktree

Before creating anything, check if a worktree already exists for this branch.

git worktree list

• If a worktree for the target branch already exists, reuse it. Report: "Reusing existing worktree at {path}" and skip to Step 4.
  • If the worktree appears in the list but is marked prunable, run git worktree prune first and proceed to create a new one.
• If the branch exists but has no worktree, ask the user: "Branch {branch} already exists. Check out existing branch, or create a new branch name?"

Step 2: Ensure .worktrees/ Directory

All worktrees live in .worktrees/ relative to the repo root.

# Get main repo root (from a worktree, returns absolute path; from main repo, returns relative .git — the cd && pwd wrapper normalizes both to absolute)
MAIN_GIT_DIR=$(git rev-parse --git-common-dir)
REPO_ROOT=$(cd "$(dirname "$MAIN_GIT_DIR")" && pwd)

# Create directory and ensure gitignored
mkdir -p "$REPO_ROOT/.worktrees"
grep -q '\.worktrees' "$REPO_ROOT/.gitignore" 2>/dev/null || echo '.worktrees/' >> "$REPO_ROOT/.gitignore"

Step 3: Create the Worktree

git worktree add "$REPO_ROOT/.worktrees/{branch}" -b {branch}

Where {branch} is the feature branch name (e.g., feature-auth or feature-auth--backend for sub-scopes).

If creation fails:

• Branch already exists: Ask user whether to check out the existing branch (git worktree add "$REPO_ROOT/.worktrees/{branch}" {branch} without -b)
• Disk/permissions error: Surface git's error message and offer fallback to working in the main repo directory

Step 4: Report

Output the result:

Worktree ready at {REPO_ROOT}/.worktrees/{branch}
Branch: {branch}

Return the worktree path so it can be passed to subsequent phases and agents.

Edge Cases

| Case | Handling | |------|---------| | Already in a worktree for this feature | Detect via git worktree list, reuse existing | | Worktree directory exists but is stale | Run git worktree prune first, then retry | | Branch name already exists | Ask user: check out existing or create new name | | Creation fails (disk/permissions) | Surface error, offer fallback to main repo |