CircleCI: run docs & coverage in first container only (#3335)

I wrote this whole complicated wofkflow-based config file, but except
in the case of a base rebuild it wouldn't really be any faster than
this simple tweak.

```
defaults: &defaults
    docker:
      - image: houqp/kobase:0.0.5
        environment:
          EMULATE_READER: 1
          # this is for shellcheck 0.4.5 and lower; can be removed for 0.4.6
          LC_ALL: en_US.UTF8

version: 2
jobs:
  install-and-build:
    <<: *defaults
    steps:
      - checkout
      - restore_cache:
          keys:
            # binary dependencies require {{ arch }} because there are different CPUs in use on the servers
            - deps-{{ arch }}-{{ checksum ".ci/install.sh" }}
      # need to init some stuff first or git will complain when sticking in base cache
      - run: git submodule init base && git submodule update base && pushd base && git submodule init && git submodule update && popd
      # we can't use command output directly for cache check so we write it to git-rev-base
      - run: pushd base && git_rev_base=$(git describe HEAD) && popd && echo $git_rev_base && echo $git_rev_base >git-rev-base
      - restore_cache:
          keys:
            - build-{{ arch }}-{{ checksum "git-rev-base" }}
      - run: echo 'export PATH=${HOME}/bin:${PATH}' >> $BASH_ENV
      - run:
          name: setup
          command: .ci/before_install.sh
      - run:
          name: install
          command: .ci/install.sh
      - save_cache:
          key: deps-{{ arch }}-{{ checksum ".ci/install.sh" }}
          paths:
            - "/home/ko/bin"
            - "/home/ko/.luarocks"
            # compiled luarocks binaries
            - "install"
      - run:
          name: fetch
          command: .ci/fetch.sh
      - run:
          name: check
          command: .ci/check.sh
      - run:
          name: build
          command: .ci/build.sh
      - save_cache:
          key: build-{{ checksum "base/git-rev" }}
          paths:
            - "/home/ko/.ccache"
            - "base"
      - persist_to_workspace:
          # Must be an absolute path, or relative path from working_directory
          root: "./"
          # Must be relative path from root
          paths:
            # front build
            - "koreader-emulator-x86_64-linux-gnu/koreader"

  test:
    <<: *defaults
    parallelism: 4
    steps:
      - checkout
      - restore_cache:
          keys:
            # binary dependencies require {{ arch }} because there are different CPUs in use on the servers
            - deps-{{ arch }}-{{ checksum ".ci/install.sh" }}
      # need to init some stuff first or git will complain when sticking in base cache
      - run: git submodule init base && git submodule update base && pushd base && git submodule init && git submodule update && popd
      # we can't use command output directly for cache check so we write it to git-rev-base
      - run: pushd base && git_rev_base=$(git describe HEAD) && popd && echo $git_rev_base && echo $git_rev_base >git-rev-base
      - restore_cache:
          keys:
            - build-{{ arch }}-{{ checksum "git-rev-base" }}
      - run: echo 'export PATH=${HOME}/bin:${PATH}' >> $BASH_ENV
      - attach_workspace:
          # Must be absolute path or relative path from working_directory
          at: "./"
      - run:
          name: test
          command: .ci/test.sh

  docs-and-coverage:
    <<: *defaults
    steps:
      - checkout
      - restore_cache:
          keys:
            # binary dependencies require {{ arch }} because there are different CPUs in use on the servers
            - deps-{{ arch }}-{{ checksum ".ci/install.sh" }}
      # need to init some stuff first or git will complain when sticking in base cache
      - run: git submodule init base && git submodule update base && pushd base && git submodule init && git submodule update && popd
      # we can't use command output directly for cache check so we write it to git-rev-base
      - run: pushd base && git_rev_base=$(git describe HEAD) && popd && echo $git_rev_base && echo $git_rev_base >git-rev-base
      - restore_cache:
          keys:
            - build-{{ arch }}-{{ checksum "git-rev-base" }}
      - run: echo 'export PATH=${HOME}/bin:${PATH}' >> $BASH_ENV
      - attach_workspace:
          # Must be absolute path or relative path from working_directory
          at: "./"
      - run:
          name: cleanup
          command: .ci/after_success.sh

workflows:
  version: 2
  build-and-test:
    jobs:
      - install-and-build
      - test:
          requires:
            - install-and-build
      - docs-and-coverage:
          requires:
            - install-and-build
```

.ci/after_success.sh

@@ -6,11 +6,13 @@ source "${CI_DIR}/common.sh"
 
 set +e
 
-# if [ "${TRAVIS_PULL_REQUEST}" = false ] && [ "${TRAVIS_BRANCH}" = 'master' ]; then
-if [ -z "${CIRCLE_PULL_REQUEST}" ] && [ "${CIRCLE_BRANCH}" = 'master' ]; then
+echo "$CIRCLE_NODE_INDEX"
+if [ ! "$CIRCLE_NODE_INDEX" = 0 ]; then
+    echo -e "\\n${ANSI_GREEN}Not on first node. Skipping documentation update and coverage."
+elif [ -z "${CIRCLE_PULL_REQUEST}" ] && [ "${CIRCLE_BRANCH}" = 'master' ]; then
     travis_retry luarocks --local install ldoc
 
-    echo -e "\n${ANSI_GREEN}Checking out koreader/doc for update."
+    echo -e "\\n${ANSI_GREEN}Checking out koreader/doc for update."
     git clone git@github.com:koreader/doc.git koreader_doc
 
     # push doc update
@@ -20,28 +22,26 @@ if [ -z "${CIRCLE_PULL_REQUEST}" ] && [ "${CIRCLE_BRANCH}" = 'master' ]; then
             echo "Failed to generate documents..."
             exit 1
         fi
-    } || exit
-    popd
+    } && popd || exit
+
     cp -r doc/html/* koreader_doc/
     pushd koreader_doc && {
         git add -A
-        echo -e "\n${ANSI_GREEN}Pushing document update..."
+        echo -e "\\n${ANSI_GREEN}Pushing document update..."
         git -c user.name="KOReader build bot" -c user.email="non-reply@koreader.rocks" \
             commit -a --amend -m 'Automated documentation build from travis-ci.'
         git push -f --quiet origin gh-pages >/dev/null
-        echo -e "\n${ANSI_GREEN}Documentation update pushed."
-    } || exit
-    popd
+        echo -e "\\n${ANSI_GREEN}Documentation update pushed."
+    } && popd || exit
 
     # rerun make to regenerate /spec dir (was deleted to prevent uploading to cache)
-    echo -e "\n${ANSI_GREEN}make all"
+    echo -e "\\n${ANSI_GREEN}make all"
     make all
     travis_retry make coverage
     pushd koreader-*/koreader && {
         # temporarily use || true so builds won't fail until we figure out the coverage issue
         luajit "$(which luacov-coveralls)" --verbose || true
-    } || exit
-    popd
+    } && popd || exit
 else
-    echo -e "\n${ANSI_GREEN}Not on official master branch, skip documentation update and coverage."
+    echo -e "\\n${ANSI_GREEN}Not on official master branch. Skipping documentation update and coverage."
 fi