I'm trying to find the source for version 3.12.20, but the current 3.12.y version on GitHub is 3.12.24. I understand I can just update my current version, but shouldn't downloading the source for my current version surely be faster?
You can do:
sudo rpi-update hash
with the hash being the kernel version from here: https://github.com/Hexxeh/rpi-firmware
sudo rpi-update ba43047bec24d5f0a4150f09a37884240f8926d2 would install