How I keep my local WordPress install up-to-date

I develop WordPress themes professionally and I need to be on the latest version of WordPress all the time. But for several reasons the "Update Now" button on the dashboard won't work locally. And I'm fine with that. Here it is how I keep my local Multisite instance of WordPress up to date.

I have a cloned version of WordPress from Github. When a new version of WordPress is out, all I do is:

1. cd into the WordPress directory
2. Pull the latest changes: git pull origin master
3. Switch the the right branch: git checkout 3.6
4. Run wpdate

Everything is up-to-date now and no other files of my installation is touched. This works seamlessly for me every time.

If you are saying to yourself what in the world is wpdate, it is just a bash alias that resides on my .bash_aliases file. Here is the code for it:

function wpdate() {
    GIT_WORK_TREE="/home/banago/Public/desk" git checkout -f;
}

Adjust the directory accordingly; it is just where my WordPress install happens to be. And by the way, I'm on Ubuntu.