detect-jujutsu

name	detect-jujutsu
description	Use at session start or before the first version control action to detect whether the repository should be operated with Git or Jujutsu (jj).
version	0.5.0

Detecting Jujutsu (jj)

This skill determines whether the current repository uses Jujutsu (jj). Use the detection ladder in order.

Trigger cues: user asks to run version control actions (for example status, diff, log, commit, amend, push, branch, rebase) where both git and jj may be available.

If jj is available in the current repo, prefer jj as the default VCS for this session unless the user or project policy explicitly asks for git.

Detection Ladder

Stop at the first successful detection.

Step 1: Try jj st (fast path)

jj st --no-pager

• Exit 0 → JJ repo. Use jj commands. Invoke use-jujutsu skill. STOP HERE.
• Blocked by tool policy → Proceed to Step 3 (do not attempt Step 2).
• Exit non-zero → Proceed to Step 2.

Step 2: Run detection script (authoritative)

The script is embedded inline to work across multiple coding agents regardless of where skills are installed.

cat > /tmp/detect-jj.sh << 'SCRIPT_EOF'
#!/bin/bash

# Embedded inline for cross-agent compatibility.
# Shared Jujutsu (jj) detection script
# Authoritative check for JJ repository status, root-aware.

QUIET=false
if [ "$1" == "--quiet" ]; then
  QUIET=true
fi

log() {
  if [ "$QUIET" = false ]; then
    echo "$1"
  fi
}

# 1. Determine repository root
REPO_ROOT=$(git rev-parse --show-toplevel 2>/dev/null)
if [ -z "$REPO_ROOT" ]; then
  log "Error: Not inside a git repository (git rev-parse failed)."
  log "Next steps: cd into a repository or run 'git status' to confirm environment."
  exit 2
fi

# 2. Check for jj command
if ! command -v jj >/dev/null 2>&1; then
  if [ -d "$REPO_ROOT/.jj" ]; then
    log "Hint: .jj directory found at repo root ($REPO_ROOT), but 'jj' command is missing."
    log "Next steps: Install Jujutsu (https://martinvonz.github.io/jj/) to work with this repository."
  else
    log "No Jujutsu detected: 'jj' command missing and no .jj directory at root."
  fi
  exit 2
fi

# 3. Authoritative check: jj status at root
if (cd "$REPO_ROOT" && jj st --no-pager --color=never >/dev/null 2>&1); then
  log "Jujutsu detected: 'jj status' succeeded at repo root ($REPO_ROOT)."
  log "Next steps: Use 'jj' commands for version control; consult 'use-jujutsu' skill for guidance."
  exit 0
else
  # Check if it was just "not a jj repo" or some other error
  if [ -d "$REPO_ROOT/.jj" ]; then
     log "Warning: .jj directory exists at root, but 'jj status' failed."
     log "Next steps: Check 'jj status' manually for specific errors (e.g. corruption or version mismatch)."
     exit 2
  else
     log "No Jujutsu detected: 'jj status' failed and no .jj directory found at root."
     log "Next steps: Use git workflows for this repository."
     exit 1
  fi
fi
SCRIPT_EOF

bash /tmp/detect-jj.sh

• Exit 0 → JJ repo. Use jj commands. Invoke use-jujutsu skill. STOP HERE.
• Exit 1 → Git repo (not JJ). Use standard git workflows. STOP HERE.
• Exit 2 → Indeterminate. Proceed to Step 3.
• Blocked by tool policy → Proceed to Step 3.

Step 3: Check for .jj/ directory (fallback - no Bash required)

Use this when Bash commands are restricted or previous steps failed.

Use the Read or Glob tool (not Bash) to check for .jj/ directory:

Determine repo root using Read on current directory or known paths:

Read: <repo-root>/.jj

• .jj/ found → JJ repo. Use jj commands. Invoke use-jujutsu skill. STOP HERE.
• Not found → Assume Git. Use standard git workflows. STOP HERE.
• Cannot determine → Ask user: "Cannot detect version control system. Is this a Jujutsu (jj) or Git repository?"

Handling Tool Restrictions

If you receive a tool policy error when running Bash:

1. Immediately switch to Step 3 (do not retry Bash commands).
2. Use Read/Glob tools only - these typically have fewer restrictions.
3. If still blocked, ask the user directly.

Outcome

• JJ confirmed: Use jj commands. Invoke use-jujutsu skill.
• Git: Use standard git workflows.
• Uncertain: State uncertainty and ask user which VCS to use.