ci: track coverage with codecov.io instead of codeclimate.com.

Comparison:

* Codecov has a simpler integration and a better UI.
* Codeclimate tracks both linter warnings (Rubocop, ESLint) and code
  coverage, but its UI for code coverage is worse than Codecov's.
* Codeclimate doesn't support Simplecov 0.18 because Codeclimate doesn't
  support 0.18's new coverage format yet.

.github/workflows/test.yaml

@@ -34,10 +34,7 @@ jobs:
       RUBYOPT: -W0 # silence ruby warnings
       VIPS_WARNING: 0 # silence libvips warnings
 
-      # Code Climate configuration. https://docs.codeclimate.com/docs/finding-your-test-coverage-token
-      CC_TEST_REPORTER_ID: ${{ secrets.CC_TEST_REPORTER_ID }}
-      GIT_COMMIT_SHA: ${{ github.sha }}
-      GIT_BRANCH: ${{ github.ref }}
+      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
 
       DATABASE_URL: postgresql://danbooru:danbooru@postgres/danbooru
       ARCHIVE_DATABASE_URL: postgresql://danbooru:danbooru@postgres/danbooru
@@ -74,7 +71,7 @@ jobs:
     - name: Install OS dependencies
       run: |
         apt-get update
-        apt-get -y install --no-install-recommends build-essential ruby ruby-dev ruby-bundler git nodejs yarnpkg webpack ffmpeg mkvtoolnix libvips-dev libxml2-dev libxslt-dev zlib1g-dev postgresql-server-dev-all wget
+        apt-get -y install --no-install-recommends build-essential ruby ruby-dev ruby-bundler git nodejs yarnpkg webpack ffmpeg mkvtoolnix libvips-dev libxml2-dev libxslt-dev zlib1g-dev postgresql-server-dev-all wget curl
         ln -sf /usr/bin/yarnpkg /usr/bin/yarn
 
     - name: Install Ruby dependencies
@@ -86,23 +83,5 @@ jobs:
     - name: Prepare database
       run: config/docker/prepare-tests.sh
 
-    # https://docs.codeclimate.com/docs/configuring-test-coverage
-    - name: Prepare test coverage for Code Climate
-      run: |
-        wget https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64
-        chmod +x test-reporter-latest-linux-amd64
-        ./test-reporter-latest-linux-amd64 before-build
-
     - name: Run tests
       run: bin/rails test
-
-    - name: Upload test coverage to Code Climate
-      if: ${{ !cancelled() }}
-      run: GIT_COMMITTED_AT="$(date -u +%s)" ./test-reporter-latest-linux-amd64 after-build --debug
-
-    # https://docs.codecov.io/docs
-    - name: Upload test coverage to Codecov.io
-      if: ${{ !cancelled() }}
-      uses: codecov/codecov-action@v1
-      with:
-        token: ${{ secrets.CODECOV_TOKEN }}