Git hook when a new branch is created and/or pushed

It's the update hook, it gets a zero sha for new refs, branches will say heads not tags

The accepted answer says to use the update hook. I'm not sure that helps everyone, as that is a server-side hook. It will work if you push your new branch, but what about keeping it purely local?

I'm creating local branches that are never pushed, so I'm using post-checkout instead. After creating your branch, aren't you typically going to check it out before doing anything else with it? When I detect a new branch, I modify it and add a commit automatically. After that, I'm able to determine if this is a new branch on a checkout by virtue of whether it has a commit history.

Here's how I do it (my hooks are in bash):

    true=1
    false=0
    
    isNewBranch()
    {   
        local logQuery=$(git log --all --not $(git rev-list --no-walk --exclude=refs/heads/$(getBranchName) --exclude=HEAD --all))  
        if [ -z $logQuery ]; then 
            echo $true
        else
            echo $false
        fi  
    }
    
    getBranchName()
    {
        echo $(git rev-parse --abbrev-ref HEAD)
    }