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

Question

I want to hook into the creation of a new branch. Either when the branch is created or when the first push is done. Is one or both possible?

Answer 1

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

Answer 2

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)
}