.PHONY: deploy
deploy: book
    @echo "====> deploying to github"
    git worktree add /tmp/book gh-pages
    rm -rf /tmp/book/*
    cp -rp html/* /tmp/book/
    cd /tmp/book && \
        git add -A && \
        git commit -m "deployed on $(shell date) by ${USER}" && \
        git push origin gh-pages