👷⭕ Add CI to build preview of the PR

👷 Changed orb used to build the page

👷 removes executor - it may not be needed

👷 Using a 🧪🐋

👷 Run 🧪 by itself without bundle (also without caching dependencies)

👷 Remove any Orb (they don't work as I think)

👷 Use an official 🧪🐋 instead (it takes forever to install it otherwise)

👷 install everything using Gemfiles and caching it

👷 to build only for UCL 🏛

👷:pencil2: Fix small error! awk was only printing, not saving the changes

👷🐛 Fix a warning shown by Jekyll and GH API

Answer provided by this answer
github/pages-gem#399 (comment)

👷 Removed the "fix" that it doesn't work and the check for errors

👷🐛 Now I was getting an empty config! awk now allows also `inplace`!

👷🐛 who knows which version of awk they have there - using classic way

i.e. creating a tmp file in between

.circleci/config.yml

@@ -0,0 +1,84 @@
+# Ruby CircleCI 2.1 configuration file
+#
+# Check https://circleci.com/docs/2.0/language-ruby/ for more details
+#
+version: 2.1
+
+jobs:
+  build:
+    docker:
+      # specify the version you desire here
+       - image: circleci/ruby:2.6.3-stretch-node
+    environment:
+      BUNDLE_PATH: ~/vendor/bundle
+
+    working_directory: ~/repo
+
+    steps:
+      - checkout
+      - run:
+          name: a merge PR
+          command: |
+            if [[ -n "${CIRCLE_PR_NUMBER}" ]]; then
+              git fetch origin +refs/pull/$CIRCLE_PR_NUMBER/merge:pr/$CIRCLE_PR_NUMBER/merge
+              git checkout -qf pr/$CIRCLE_PR_NUMBER/merge
+            fi
+
+      - run:
+          name: Which bundler/jekyll? create gemfile
+          command: |
+            bundle -v
+            printf "source 'https://rubygems.org'\nrequire 'json'\nrequire 'open-uri'\nversions = JSON.parse(open('https://pages.github.com/versions.json').read)\n\ngem 'github-pages', group: :jekyll_plugins\ngem 'html-proofer'" > Gemfile
+            cat Gemfile
+
+      # Download and cache dependencies
+      - restore_cache:
+          keys:
+          - rubygems-v1-latest
+
+      - run:
+          name: install dependencies
+          command: bundle check || bundle install --jobs=4 --retry=3
+
+      # - run:
+      #     name: Use center settings
+      #     command: |
+      #       title='# Example: Name of your cluster, Name University'
+      #       awk -v beg="${title}" -v num=8 '$0==beg{c=num} c&&c--{sub(/# /,"")} 1' _config.yml > tmp_config.yml
+      #       mv -f tmp_config.yml _config.yml
+
+      - run:
+          name: Jekyll build
+          command: bundle exec jekyll build -d html 2> std.err
+
+      - run:
+          name: Check Jekyll build
+          command: cat std.err
+
+      - run:
+          name: Jekyll re-build for local
+          command: |
+            echo "url: https://${CIRCLE_BUILD_NUM}-30926520-gh.circle-artifacts.com" > circle.yml && \
+            bundle exec jekyll build -d html -b "/0/html"  --config _config.yml,circle.yml && \
+            find ./html/ -type f -iname '*html' | xargs -I{} sed -i \
+              -e 's|href="\(\.\/.*\/\)"|href="\1index.html"|g' \
+              -e '/0\/html/ s|href="\(\/.*\/\)"|href="\1index.html"|g' {}
+            # Replace pages ending on `/` from our site to direct to index.html
+
+      - run:
+          name: "Built documentation is available at:"
+          command: DOCS_URL="${CIRCLE_BUILD_URL}/artifacts/${CIRCLE_NODE_INDEX}/html/index.html"; echo $DOCS_URL
+
+      - save_cache:
+          paths:
+            - ~/vendor/bundle
+          key: rubygems-v1-latest
+
+      # collect reports
+      - store_artifacts:
+          path: ~/repo/html
+          destination: html
+
+notify:
+  webhooks:
+    - url: https://giles.cadair.dev/circleci