Clean Up Stale Local Git Branches

#!/bin/bash

# This script cleans up local Git branches that have been merged
# into the current branch (e.g., 'main' or 'master') or whose remote tracking branch no longer exists.

# Set default main branch name
MAIN_BRANCH="main"

# Check if current directory is a git repository
if ! git rev-parse --is-inside-work-tree > /dev/null 2>&1; then
  echo "Error: Not a Git repository."
  exit 1
fi

# Fetch latest remote changes to update local tracking branches
echo "Fetching latest remote changes..."
git fetch --prune

echo "Deleting local branches merged into '$MAIN_BRANCH'...
"
# List merged branches, excluding main/master and currently checked out branch
CURRENT_HEAD=$(git rev-parse --abbrev-ref HEAD)
MERGED_BRANCHES=$(git branch --merged "$MAIN_BRANCH" | grep -v "$MAIN_BRANCH" | grep -v "$CURRENT_HEAD" | sed 's/^\s*//')

if [ -z "$MERGED_BRANCHES" ]; then
  echo "No merged branches to delete."
elif [ -n "$MERGED_BRANCHES" ]; then
  echo "$MERGED_BRANCHES" | xargs -r git branch -d
  echo "Merged branches cleanup complete."
fi

echo "
Deleting local branches whose remote tracking branch no longer exists..."

# Identify and delete stale remote tracking branches
# This command prunes local branches that no longer have a remote counterpart
STALE_REMOTE_TRACKING_BRANCHES=$(git remote prune origin --dry-run | grep 'would prune' | awk '{print $NF}')
if [ -n "$STALE_REMOTE_TRACKING_BRANCHES" ]; then
  echo "The following remote tracking branches would be pruned (dry run):"
  echo "$STALE_REMOTE_TRACKING_BRANCHES"
  read -p "Execute actual prune? (y/N): " -n 1 -r
  echo # (optional) move to a new line
  if [[ $REPLY =~ ^[Yy]$ ]]
  then
    git remote prune origin
    echo "Stale remote tracking branches pruned."
  else
    echo "Skipping actual remote prune."
  fi
else
  echo "No stale remote tracking branches to prune."
fi

echo "
Git cleanup script finished."