git-guardian

name	git-guardian
version	1.0.0
author	Polycat
tags	["git","security","secrets","pre-commit","safety","devops"]
license	MIT
platform	universal
description	Pre-commit safety checks for AI-assisted development. Detects secrets, large files, merge conflict markers, sensitive files, and common AI-coding mistakes before they hit your repo.

🛡️ Git Guardian

Compatible with Claude Code, Codex CLI, Cursor, Windsurf, and any SKILL.md-compatible agent.

Pre-commit safety checks built for AI-assisted development. AI agents generate code fast — sometimes too fast. Git Guardian catches secrets, sensitive files, merge conflicts, and common AI mistakes before they land in your history.

---

Triggers

Activate this skill when:

• "check before commit", "is this safe to commit", "pre-commit check"
• "any secrets in staged files?", "check for API keys"
• About to commit AI-generated code
• "run git guardian", "safety check", "audit staged changes"
• After a large AI-generated code dump, before pushing
• User sets up a new repo and wants pre-commit safety

---

The Full Check Suite

Run these checks against staged changes (or a specified path). Report findings with severity: 🔴 BLOCK, 🟡 WARN, 🔵 INFO.

---

Check 1: Secret Detection 🔴

Patterns that indicate leaked credentials:

# Check staged files for secrets
git diff --cached --name-only | while read f; do
  echo "=== $f ==="
  git show ":$f" 2>/dev/null
done | grep -inE \
  'api[_-]?key|apikey|api[_-]?secret|\
secret[_-]?key|secret[_-]?token|\
auth[_-]?token|access[_-]?token|bearer[_-]?\
private[_-]?key|ssh[_-]?key|rsa[_-]?private|\
password\s*=\s*["\x27][^\x27"]{6,}|\
passwd\s*=\s*["\x27][^\x27"]{6,}|\
aws_access_key_id|aws_secret_access_key|\
AKIA[0-9A-Z]{16}|\
ghp_[a-zA-Z0-9]{36}|github_pat_|\
sk-[a-zA-Z0-9]{32,}|\
xoxb-|xoxa-|xoxp-|\
glpat-|glcpat-|\
npm_[a-zA-Z0-9]{36}|\
-----BEGIN (RSA|EC|DSA|OPENSSH) PRIVATE KEY'

High-risk literal patterns to check for:

# Check for raw high-entropy strings (possible tokens/keys)
git diff --cached | grep "^+" | grep -vE "^(\\+\\+\\+)" | \
  grep -E '[a-zA-Z0-9+/]{40,}={0,2}' | \
  grep -vE '(hash|sha|digest|checksum|fingerprint|base64|encoded|example|placeholder|YOUR_|REPLACE_|<.*>)' | \
  head -20

Common secret formats by provider:

Provider	Pattern	Example prefix
OpenAI	sk-[a-zA-Z0-9]{48}	sk-proj-...
Anthropic	sk-ant-[a-zA-Z0-9-]{95}	sk-ant-api03-...
GitHub	ghp_[a-zA-Z0-9]{36}	ghp_abc...
AWS	AKIA[A-Z0-9]{16}	AKIAIOSFODNN7...
Google API	AIza[0-9A-Za-z-_]{35}	AIzaSy...
Slack	xoxb-[0-9-]{50,}	xoxb-123-...
Stripe	sk_live_[a-zA-Z0-9]{24}	sk_live_...
Twilio	SK[a-zA-Z0-9]{32}	SK1234...
JWT	eyJ[a-zA-Z0-9-_]+\.[a-zA-Z0-9-_]+\.	eyJhbGc...

Severity: 🔴 BLOCK — never commit real credentials. If found:

1. Remove the secret from staged files
2. Rotate the credential immediately — assume it's compromised
3. Use environment variables, a secrets manager, or .env (gitignored)

---

Check 2: Sensitive File Detection 🔴

# Check if sensitive file types are staged
git diff --cached --name-only | grep -iE \
  '\.(env|pem|key|p12|pfx|jks|keystore|ppk|ovpn)$|
  ^\.env(\.|$)|
  \.env\.(local|production|staging|dev|test)$|
  id_rsa|id_dsa|id_ecdsa|id_ed25519|
  \.ssh/|
  credentials$|credentials\.json|
  secrets\.json|secrets\.yaml|secrets\.yml|
  \.netrc$|
  wp-config\.php|
  database\.yml$|
  settings\/local\.py|
  config\/secrets\.'

Never commit these:

• .env files with real values
• Private key files (.pem, .key, .p12, .ppk)
• SSH private keys (id_rsa, id_ed25519, etc.)
• VPN configs (.ovpn)
• credentials.json (Google service accounts)
• secrets.yaml / secrets.yml

Severity: 🔴 BLOCK — add to .gitignore immediately.

---

Check 3: Large Files 🟡

# Find staged files over 1MB
git diff --cached --name-only | while read f; do
  size=$(git cat-file -s ":$f" 2>/dev/null || echo 0)
  if [ "$size" -gt 1048576 ]; then
    echo "LARGE: $f ($(( size / 1024 ))KB)"
  fi
done

Thresholds:

• 1MB: 🟡 WARN — is this intentional? Should it be in .gitignore or git-lfs?

• 10MB: 🔴 BLOCK — almost certainly wrong. Binary, dataset, or dependency artifact.

• 50MB: 🔴 BLOCK — will fail on GitHub/GitLab push limits.

Common large file mistakes:

• node_modules/ committed by accident
• Binary build artifacts (dist/, build/, *.pyc, *.class)
• Datasets or fixtures that should be downloaded at runtime
• Media files (images, video) that should use git-lfs or external storage

---

Check 4: Merge Conflict Markers 🔴

# Detect unresolved merge conflicts in staged files
git diff --cached --name-only | while read f; do
  if git show ":$f" 2>/dev/null | grep -qE '^(<{7}|>{7}|={7}|[|]{7}) '; then
    echo "CONFLICT MARKERS: $f"
    git show ":$f" | grep -nE '^(<{7}|>{7}|={7}|[|]{7}) ' | head -5
  fi
done

Markers to detect:

• <<<<<<< HEAD
• =======
• >>>>>>> branch-name
• ||||||| merged common ancestors (diff3 style)

Severity: 🔴 BLOCK — code with conflict markers will not compile or run.

---

Check 5: TODO/FIXME/HACK in New Code 🔵

# Find new lines with quality flags in staged diff
git diff --cached | grep "^+" | grep -vE "^\+\+\+" | \
  grep -iE '\b(TODO|FIXME|HACK|XXX|BUG|TEMP|KLUDGE|NOCOMMIT)\b' | \
  head -20

Severity: 🔵 INFO — not a blocker, but worth knowing what's going in.

Special case — 🔴 BLOCK on NOCOMMIT:

git diff --cached | grep "^+" | grep -iE '\bNOCOMMIT\b'

If found, stop — this was intentionally marked to not be committed.

---

Check 6: .gitignore Coverage Audit 🟡

# Check if common sensitive paths are covered by .gitignore
cat .gitignore 2>/dev/null | sort > /tmp/gi_current.txt

echo "Checking .gitignore coverage..."

patterns=(
  "*.env"
  ".env"
  ".env.*"
  "*.pem"
  "*.key"
  "*.p12"
  "id_rsa"
  "id_ed25519"
  "*.log"
  "node_modules/"
  "__pycache__/"
  "*.pyc"
  "dist/"
  "build/"
  ".DS_Store"
  "Thumbs.db"
  "*.sqlite"
  "*.sqlite3"
  "venv/"
  ".venv/"
  "*.orig"
  "secrets.*"
  "credentials.json"
)

for p in "${patterns[@]}"; do
  if ! grep -qF "$p" .gitignore 2>/dev/null; then
    echo "MISSING: $p"
  fi
done

Severity: 🟡 WARN for missing patterns — add them before the next commit touches those file types.

Recommended .gitignore additions for AI-assisted projects:

# Secrets & credentials
.env
.env.*
!.env.example
*.pem
*.key
*.p12
*.pfx
*.ppk
id_rsa
id_ed25519
id_ecdsa
credentials.json
secrets.yaml
secrets.yml
.netrc

# AI agent artifacts (if applicable)
.agent_memory/
agent_logs/
session_*.json

# Common build artifacts
node_modules/
dist/
build/
__pycache__/
*.pyc
*.pyo
.venv/
venv/
*.egg-info/

# OS
.DS_Store
Thumbs.db
*.orig

---

Check 7: Accidental Debug Code 🔵

# Detect common debug artifacts in staged diff
git diff --cached | grep "^+" | grep -vE "^\+\+\+" | \
  grep -iE \
  'console\.log\(|print\(f?["\x27](debug|test|tmp|REMOVE|DELETE ME)|\
debugger;|\
pdb\.set_trace|breakpoint\(\)|\
binding\.pry|\
var_dump\(|die\(|exit\(1\)' | \
  head -20

Severity: 🔵 INFO — common in AI-generated code. Review before merging to main.

---

Full Run Command

Run the complete suite against currently staged changes:

echo "🛡️  Git Guardian — Pre-Commit Safety Check"
echo "==========================================="
echo ""

# 1. What's staged?
echo "📋 Staged files:"
git diff --cached --name-only
echo ""

# 2. Run checks (see above for full implementations)
echo "🔴 Check 1: Secrets..."
echo "🔴 Check 2: Sensitive files..."
echo "🟡 Check 3: Large files..."
echo "🔴 Check 4: Merge conflict markers..."
echo "🔵 Check 5: TODO/FIXME/NOCOMMIT..."
echo "🟡 Check 6: .gitignore coverage..."
echo "🔵 Check 7: Debug artifacts..."

---

Output Format

🛡️  Git Guardian — Pre-Commit Safety Check
===========================================
Staged files: 4 | Checks: 7 | Time: 0.3s

🔴 BLOCKED (2 issues — fix before committing)
─────────────────────────────────────────────
[1] SECRET DETECTED in src/config.py (line 14)
    OPENAI_API_KEY = "sk-proj-abc123..."
    → Remove key, rotate immediately, use env var

[2] MERGE CONFLICT MARKERS in src/api/routes.py
    Line 47: <<<<<<< HEAD
    Line 52: >>>>>>> feature/auth-refactor
    → Resolve conflict before committing

🟡 WARNINGS (1 issue — review recommended)
──────────────────────────────────────────
[3] LARGE FILE: data/fixtures.json (8.2MB)
    → Add to .gitignore or move to git-lfs

🔵 INFO (3 notes)
─────────────────
[4] TODO found in src/auth.py (line 88)
    # TODO: add rate limiting here
[5] console.log found in frontend/app.ts (line 23)
[6] .gitignore missing: *.pem, .env.*

══════════════════════════════════════════
❌ COMMIT BLOCKED — resolve 2 critical issue(s) first

🛡️  Git Guardian — Pre-Commit Safety Check
===========================================
Staged files: 3 | Checks: 7 | Time: 0.2s

✅ All checks passed — safe to commit

---

Installing as a Git Hook

To run automatically before every commit in a project:

cat > .git/hooks/pre-commit << 'EOF'
#!/bin/bash
# Git Guardian pre-commit hook
# Runs basic safety checks before allowing commit

# Check for secrets
if git diff --cached | grep -qiE 'api[_-]?key\s*=\s*["\x27][^\x27"]{10,}|AKIA[0-9A-Z]{16}|sk-[a-zA-Z0-9]{32,}|ghp_[a-zA-Z0-9]{36}'; then
  echo "🔴 Git Guardian: Possible secret detected in staged changes"
  echo "   Run a full check: ask your AI agent to run git-guardian"
  exit 1
fi

# Check for merge conflict markers
if git diff --cached | grep -qE '^(<{7}|>{7}|={7}) '; then
  echo "🔴 Git Guardian: Merge conflict markers detected"
  exit 1
fi

# Check for NOCOMMIT
if git diff --cached | grep -qiE '\bNOCOMMIT\b'; then
  echo "🔴 Git Guardian: NOCOMMIT marker found — this change was flagged to not be committed"
  exit 1
fi

echo "✅ Git Guardian: Basic checks passed"
exit 0
EOF

chmod +x .git/hooks/pre-commit
echo "✅ Git Guardian pre-commit hook installed"

---

Why This Matters for AI-Assisted Development

AI coding tools are fast — sometimes too fast. Common failure modes:

1. Context leakage — agent reads a .env file for context, then writes the values into generated code
2. Conflict confusion — agent sees conflict markers and treats them as code, writes around them instead of resolving
3. Overeager staging — git add . after AI-generated files includes things that should be ignored
4. Debug trails — AI includes console.log, print, breakpoint() for its own reasoning, forgets to remove them
5. Fixture bloat — AI generates large test fixtures inline instead of loading from external source

Git Guardian is your last line of defense before those mistakes become permanent history.