Shell script that deletes local git branches that were deleted on the remote

pruneLocalBranches.sh

#!/bin/zsh

# Deletes local branches that have been deleted on the remote
function pruneLocalBranches {
    # Get the main branch name (the one checked out on the remote)
    mainBranch=$(git rev-parse --abbrev-ref origin/HEAD | cut -d "/" -f 2)

    # Check out that branch because it should never get pruned
    git checkout $mainBranch &> /dev/null

    # Prune branches
    git fetch origin --prune &> /dev/null

    # List branches that have been removed from origin and write to file
    git branch -vv | awk '/: gone]/{print $1}' > /tmp/branchesToPurge

    # Open the file for editing
    vim /tmp/branchesToPurge

    # Print list of branches to be deleted
    echo "The following branches will be deleted:"
    cat /tmp/branchesToPurge

    # Ask if we should proceed
    answer=''
    vared -p "Are you sure you want to delete these branches (y/n)? " -c answer
    case ${answer:0:1} in
        y|Y )
            echo "Deleting...";
            # Delete branches listed in file
            xargs git branch -D < /tmp/branchesToPurge;;
        * )
            echo "Aborted";;
    esac
}