Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/usewhale/whale/using-git-worktreesnpx skills add usewhale/Whale --skill using-git-worktreesgit clone --depth 1 https://github.com/usewhale/WhaleWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00036 | $0.01896 |
| Opus 5 | $0.00018 | $0.00948 |
| Sonnet 5 | $0.00007 | $0.00379 |
| Haiku 4.5 | $0.00004 | $0.00190 |
Grade A, and why
using-git-worktrees scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
91% identical to using-git-worktrees — 31 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 216 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Using Git Worktrees
Overview
Ensure work happens in an isolated workspace. Prefer your platform's native worktree tools. Fall back to manual git worktrees only when no native tool is available.
Core principle: Detect existing isolation first. Then use native tools. Then fall back to git. Never fight the harness.
Announce at start: "I'm using the using-git-worktrees skill to set up an isolated workspace."
Step 0: Detect Existing Isolation
Before creating anything, check if you are already in an isolated workspace.
GIT_DIR=$(cd "$(git rev-parse --git-dir)" 2>/dev/null && pwd -P)
GIT_COMMON=$(cd "$(git rev-parse --git-common-dir)" 2>/dev/null && pwd -P)
BRANCH=$(git branch --show-current)
Submodule guard: GIT_DIR != GIT_COMMON is also true inside git submodules. Before concluding "already in a worktree," verify you are not in a submodule:
# If this returns a path, you're in a submodule, not a worktree — treat as normal repo
git rev-parse --show-superproject-working-tree 2>/dev/null
If GIT_DIR != GIT_COMMON (and not a submodule): You are already in a linked worktree. Skip to Step 3 (Project Setup). Do NOT create another worktree.
Report with branch state:
- On a branch: "Already in isolated workspace at
<path>on branch<name>." - Detached HEAD: "Already in isolated workspace at
<path>(detached HEAD, externally managed). Branch creation needed at finish time."
If GIT_DIR == GIT_COMMON (or in a submodule): You are in a normal repo checkout.
Has the user already indicated their worktree preference in your instructions? If not, ask for consent before creating a worktree:
"Would you like me to set up an isolated worktree? It protects your current branch from changes."
Honor any existing declared preference without asking. If the user declines consent, work in place and skip to Step 3.
Step 1: Create Isolated Workspace
You have two mechanisms. Try them in this order.
1a. Native Worktree Tools (preferred)
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 216 lines · 36 tokens per session scan A 085a45ee3de4
using-git-worktrees is a skill published in the GitHub repository usewhale/Whale (924 stars, last pushed 22d ago), licensed MIT. It adds 36 tokens to every session and 1,896 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 91% identical to using-git-worktrees, differing in 31 lines, and is treated as a copy.
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