isolate Skill

Using 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.
Never create a worktree without verifying it's gitignored.

Steps

Step 1: Directory Selection

Follow this priority order:

1. Check existing directories:

   ls -d .worktrees 2>/dev/null     # Preferred (hidden)
   ls -d worktrees 2>/dev/null      # Alternative
   

   If found: Use that directory. .worktrees wins if both exist.

2. Check CLAUDE.md:

   grep -i "worktree.*director" CLAUDE.md 2>/dev/null
   

   If preference specified: Use it without asking.

3. Ask user (only if no directory exists and no preference):

   No worktree directory found. Where should I create worktrees?
   1. .worktrees/ (project-local, hidden)
   2. ~/.config/tn/worktrees/<project-name>/ (global location)
   

Step 2: Safety Verification

MUST verify directory is ignored before creating worktree:

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

If NOT ignored: Add to .gitignore and commit.

Step 3: Create Worktree

1. Detect project name: project=$(basename "$(git rev-parse --show-toplevel)")
2. Create worktree: git worktree add "$path" -b "$BRANCH_NAME"
3. Run project setup (auto-detect from package.json, Cargo.toml, etc.)
4. Verify clean baseline (run tests)
5. Record the baseline state (passing test count / suite output) so later tn:gate or tn:audit can compare against it
6. Report location

If no test command exists: degrade gracefully — record "no tests; baseline = clean checkout + setup completes" and note it in the report. Do not block isolation on a project that legitimately has no tests.

Red Flags

Thought	Reality
"Directory doesn't need gitignore"	Unignored worktrees pollute version control
"Skip baseline tests, just start"	Baseline test failure means environment issues — must resolve first
"Develop directly on the current branch"	Unisolated development pollutes the main branch
"Worktree is done once created"	Must verify the test baseline passes before starting work

Quick Reference

Dimension	Key point
Directory priority	.worktrees → worktrees → CLAUDE.md → ask user
Safety check	Must verify gitignore
Baseline verification	Run tests after creation to ensure clean
Cleanup	Handled by tn:ship

Next Step

When done:

• Normal case → return to caller (usually tn:assemble or tn:forge), continue implementation flow
• Baseline tests fail → report failure reason, ask user whether to continue
• User requests stop → end the current flow

Guardrails

• Never create a worktree without verifying the directory is gitignored
• If baseline tests fail, report and ask — don't proceed silently
• Follow existing directory conventions if they exist
• Announce at start: "I'm using the tn:isolate skill to set up an isolated workspace."
• Pairs with tn:ship for cleanup after work is complete