🔍 `post-checkout` Hook — What Does It Do?

The post-checkout hook is triggered immediately after a successful checkout — whether it's switching branches, checking out a commit, or restoring files.

Location: .git/hooks/post-checkout
✅ It cannot stop or undo the checkout; it’s purely for automation and notifications.

📥 Arguments Passed to the Hook

When the post-checkout hook is triggered, Git passes the following arguments:

post-checkout <old HEAD> <new HEAD> <is_branch_checkout>

Argument	Meaning
`$1`	Old commit hash
`$2`	New commit hash
`$3`	`1` if it was a branch switch, `0` if file checkout

🎯 Real-World Use Cases of `post-checkout` Hook

1. 🧪 Run Setup Script on Branch Switch

Auto-run setup when switching branches:

#!/bin/bash

if [ "$3" == "1" ]; then
  echo "📦 You switched branch! Running setup..."
  if [ -f setup.sh ]; then
    bash setup.sh
  fi
fi

2. 🔃 Auto Copy `.env` File Based on Branch

Automatically load the environment configuration for the active branch:

#!/bin/bash

branch=$(git rev-parse --abbrev-ref HEAD)
cp ".env.$branch" .env 2>/dev/null && echo "✅ Loaded .env.$branch" || echo "ℹ️ No .env file for $branch"

3. 🧹 Clear Cache or Temporary Files

Remove any temporary files or folders after a checkout:

#!/bin/bash
rm -rf .cache dist tmp/
echo "🧹 Cleared local build/cache folders."

4. 🔔 Show Notifications on Branch Switch

Display a terminal or system notification for awareness:

#!/bin/bash
branch=$(git rev-parse --abbrev-ref HEAD)
echo "🔔 Switched to branch: $branch"

5. 🧾 Log Checkout Events

Keep a log of all checkout activities:

#!/bin/bash
echo "$(date) - Switched from $1 to $2 (Branch: $3)" >> .checkout-history.log

6. 🖥️ Branch-Specific Warnings or Setup

Display a warning if you switch to production or sensitive branches:

#!/bin/bash
branch=$(git rev-parse --abbrev-ref HEAD)

if [[ "$branch" == "prod" ]]; then
  echo "🛡️ WARNING: You are on PRODUCTION branch"
fi

📦 Summary Table

Use Case	Benefit
Run setup after branch switch	Auto-install or re-init environment
Auto copy env files	Avoid manual `.env` handling
Clear temp/cache files	Clean workspace every time
Show notifications on checkout	Improve developer awareness
Log branch checkout activity	Enable auditing or debugging
Warn on sensitive branches	Prevent accidental changes to `prod`

🧠 Visual Flow (Mermaid Diagram)

🔚 Final Thoughts

The post-checkout hook is not about blocking changes — it’s about triggering intelligent automation after switching code contexts.
Perfect for automated setups, env handling, and developer guidance.
Lightweight, powerful, and beginner-friendly.

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🔍 post-checkout Hook — What Does It Do?