0 Automate Your Git User Setup with a Post-Checkout Hook.md

Automate Your Git User Setup with a Post-Checkout Hook

When you work across multiple repositories—or switch between personal and work projects—it’s easy to forget which Git identity (name and email) a repo should use. This simple Git hook helps by prompting you to pick a past author identity whenever you check out a branch, then automatically sets user.name and user.email for that repository.

What This Hook Does

• Runs after every git checkout.
• If the repository already has a local user.name and user.email, it does nothing.
• Otherwise, it scans the repo’s history for author names/emails, shows them in an interactive picker (fzf), and lets you choose.
• It then writes the chosen identity to the repo’s local config.

Requirement: You’ll need fzf installed for the interactive picker.

One-Time Setup

1. Create a directory for your hooks

   mkdir -p ~/.config/git/hooks

2. Save the script as post-checkout

   • Path: ~/.config/git/hooks/post-checkout
   • Contents: (see script below)

3. Make it executable

   chmod +x ~/.config/git/hooks/post-checkout

4. Tell Git to use your hooks directory

   git config --global core.hooksPath ~/.config/git/hooks

Now this hook will run for any repository using your global Git config.

How It Works (Briefly)

• git config --local --get … checks if the repo already defines a user—if yes, the script exits quietly.
• git log --format='%an %ae' lists author names/emails from commit history.
• The pipeline (sort | uniq -c | sed | sort -n -k 1 -r) deduplicates, counts, and ranks identities by frequency so your most-used identities appear first.
• fzf provides an interactive selection UI.
• The chosen name and email are written to the repo’s local config with git config --local.

Tips

• If you frequently switch identities, consider adding more hooks (e.g., post-commit) with similar logic.

• You can prefill defaults by setting global values:

  git config --global user.name "Your Name"
  git config --global user.email "you@example.com"

  The hook only overrides when a repo has no local setting.

That’s it—enjoy faster, safer identity switching across your Git projects!

post-checkout

#!/bin/bash

name="$(git config --local --get user.name)"
email="$(git config --local --get user.email)"

if [[ ! ( -z "$name" || -z "$email" ) ]]; then
  exit
fi

selected=$(git shortlog -sne "$2" \
  | sed -e 's/^[[:space:]]\+//g; s/[[:space:]]\+/ /g' \
  | fzf --prompt "Git account>" )

# --- Selection check ---
if [[ -z "$selected" ]]; then
  echo "Canceled."
  exit 1
fi

# --- Extract name and email ---
# Use sed to extract "name" and "email"
name="$(echo "$selected" | sed -e 's/^[0-9]\+[[:space:]]\+//g; s/[[:space:]]*<.*>$//g;')"
email="$(echo "$selected" | sed -e 's/^.*<//g; s/>$//g')"

# --- Set git config ---
git config --local user.name "$name"
git config --local user.email "$email"

echo "\
✅ Configuration complete:
   user.name  = $name
   user.email = $email"