This site uses my custom ath-tufte-hugo theme as a submodule.
When cloning for the first time, use this command to get the theme too:
git clone --recursive https://github.com/andrewheiss/ath-tufte-hugo.git
To get the theme later, use this command:
git submodule add \
https://github.com/andrewheiss/ath-tufte-hugo.git \
themes/ath-tufte-hugo
To update to the latest version of the theme, use:
git submodule update --recursive --remote