From GitHub via a shell script it is simple to get the unstable master branch:
git clone git://github.com/WordPress/WordPress.git
But how can I get the highest numbered stable release via a script, not by manually checking out the code, but using a deployment shell script or a deployment tool such as Fabric?
From a Fabric fabfile I have on GitHub:
git clone git://github.com/WordPress/WordPress.git .
git checkout $(git describe --tags $(git rev-list --tags --max-count=1))
It clones the repo like normal, then does some shell magic to find the latest tagged version of WordPress (which is where the stable branches live).