arc-using-worktrees

arc-using-worktrees

When to Use

Create an isolated workspace for a single epic. This skill is a thin wrapper around arcforge expand --epic <id> — it does not create worktrees by hand.

For multi-epic batch expansion, use arc-coordinating expand instead.

REQUIRED BACKGROUND: arc-using — read the Worktree Rule for the three norms (no hardcoded paths, no manual git worktree add, enter via arcforge status --json).

Core Workflow

Step 1: Identify the epic

Read the epic id from dag.yaml or the user's request. Abort if the epic id is unknown — you cannot create a worktree for an epic that is not in the DAG.

Step 2: Delegate to coordinator

node "${SKILL_ROOT}/scripts/coordinator.js" expand --epic <epic-id> --project-setup

What this does (single authoritative implementation in ${ARCFORGE_ROOT}/scripts/lib/coordinator.js):

• Derives the canonical worktree path via ${ARCFORGE_ROOT}/scripts/lib/worktree-paths.js (~/.arcforge/worktrees/<project>-<hash>-<epic>/).
• Runs git worktree add <path> -b <epic-id>.
• Writes the .arcforge-epic marker with base worktree + base branch.
• Auto-detects the project installer (package.json → npm install, pyproject.toml → pip install -e ., Cargo.toml → cargo build, go.mod → go mod download) when --project-setup is passed.
• Updates dag.yaml epic status and worktree field.

Step 3: Read the returned path

The command prints JSON. Read the path field — do not reconstruct it from pattern knowledge, and do not hardcode it in subsequent messages.

Step 4: Report to the user

Use the completion format below, filling the absolute path from the command output.

Red Flags

Stop immediately if you catch yourself thinking:

1. "I'll just git worktree add it directly" — NO. Bypasses the .arcforge-epic marker and dag.yaml update that arc-coordinating sync depends on, producing silently broken state.
2. "I'll put it somewhere convenient like ./worktrees/" — NO. The canonical path is derived at runtime; putting it elsewhere makes every downstream tool fail to find it.
3. "I'll hardcode ~/.arcforge/worktrees/... in my output" — NO. Read the path field from the CLI's JSON output. The derivation rule has evolved before and will evolve again.
4. "I'll skip the dag.yaml check" — NO. If the epic is not in the DAG, arcforge expand will refuse and that refusal is correct.
5. "The CLI failed, so I'll do it manually" — NO. A CLI failure is a real problem, not a prompt to bypass the mechanism. Report blocked.

Stage Completion Format

─────────────────────────────────────────────────
✅ Worktree created for <epic-id>

Path: <absolute path from arcforge expand JSON>
Branch: <epic-id>
Tracking: .arcforge-epic

Next: cd to the path, then use `/arc-finishing-epic` when work is complete
─────────────────────────────────────────────────

Blocked Format

─────────────────────────────────────────────────
⚠️ Worktree creation blocked

Epic: <epic-id>
Reason: <stderr from arcforge expand>

Common causes:
- Epic not in dag.yaml
- Epic not ready (dependencies incomplete)
- Git worktree add failed (uncommitted changes, branch conflict)

Report the exact CLI error and stop.
─────────────────────────────────────────────────

Related Skills

• Called by: arc-coordinating (when a single epic needs expansion), arc-agent-driven, arc-executing-tasks
• After this skill: Work in the created worktree, then /arc-finishing-epic to integrate
• Alternative: arc-coordinating expand (batch mode — all ready epics at once, no --epic flag)