Use Travis CI to test the book build and then deploy it to the site, take 2

.travis.yml

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+dist: trusty
+sudo: false
+
+language: node_js
+node_js:
+  - "4"
+
+# cache:
+#   directories:
+#     - node_modules
+
+install:
+  - npm install gitbook-cli -g
+  - gitbook install
+
+before_script:
+  - mkdir -p "${TRAVIS_BUILD_DIR}"/build
+
+script:
+  - gitbook build . "${TRAVIS_BUILD_DIR}"/build
+  - env | sort
+  - |
+    if [[ "${TRAVIS_BRANCH}" == master && "${TRAVIS_PULL_REQUEST}" == false ]]; then
+        # Commits to master that are not pull requests, that is, only
+        # actual addition of code to master, should deploy the book to
+        # the site.
+        bash "${TRAVIS_BUILD_DIR}"/tools/deploy/update_site_travis.bash
+    fi

tools/deploy/update_site_travis.bash

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+#!/usr/bin/env bash
+
+# update_site_travis.bash: Update a GitHub repo with the book build
+# products.
+
+set -o errexit
+
+# Required environment variables:
+# - DOCS_BRANCH_NAME: name of the remote branch serving the book
+# - DOCS_REPO_NAME: name of the remote repo
+# - DOCS_REPO_OWNER: name of the remote repo's owner
+# - GH_TOKEN: [secret] Personal Access Token
+
+bold=$(tput bold)
+normal=$(tput sgr0)
+
+if [ -z ${DOCS_BRANCH_NAME+x} ]; then
+    echo "${bold}\$DOCS_BRANCH_NAME is not set!${normal}"
+    exit 1
+elif [ -z ${DOCS_REPO_NAME+x} ]; then
+    echo "${bold}\$DOCS_REPO_NAME is not set!${normal}"
+    exit 1
+elif [ -z ${DOCS_REPO_OWNER+x} ]; then
+    echo "${bold}\$DOCS_REPO_OWNER is not set!${normal}"
+    exit 1
+elif [ -z ${GH_TOKEN+x} ]; then
+    echo "${bold}\$GH_TOKEN is not set!${normal}"
+    exit 1
+fi
+
+git config user.name "Travis CI User"
+git config user.email "travis@travis-ci.org"
+
+GH_REPO_REF="github.com/${DOCS_REPO_OWNER}/${DOCS_REPO_NAME}.git"
+
+# Assume the book has already been built, and was moved to `build/`
+# inside the same directory as this script.
+
+if [ -d build ]; then
+    echo "${bold}Cloning the website repo...${normal}"
+    git clone -b "${DOCS_BRANCH_NAME}" https://git@"${GH_REPO_REF}"
+    rm -rf ./"${DOCS_REPO_NAME}"/*
+    cp -a ./build/* ./"${DOCS_REPO_NAME}"
+    pushd ./"${DOCS_REPO_NAME}"
+    echo "www.algorithm-archive.org" > CNAME
+    echo "${bold}Adding changes...${normal}"
+    git add --all
+    echo "${bold}Committing...${normal}"
+    # This will return 1 if there are no changes, which should not
+    # result in failure.
+    git commit \
+        -m "Deploy book to GitHub Pages Travis build: ${TRAVIS_BUILD_NUMBER}" \
+        -m "Commit: ${TRAVIS_COMMIT}" || ret=$?
+    git push "https://${GH_TOKEN}@${GH_REPO_REF}"
+    popd
+else
+    echo "" >&2
+    echo "${bold}Warning: The book wasn't found!${normal}" >&2
+    echo "${bold}Warning: Not going to push the book to GitHub!${normal}" >&2
+    exit 1
+fi