fixup! Move RSpec 4 into a separate job

Author: pirj

.github/workflows/main.yml

@@ -61,3 +61,24 @@ jobs:
           ruby-version: "${{ matrix.ruby }}"
           bundler-cache: true
       - run: bundle exec rake ${{ matrix.task }}
+
+  rspec4:
+    runs-on: ubuntu-latest
+    name: RSpec 4
+    steps:
+      - uses: actions/checkout@v2
+      - name: Use latest RSpec 4 from `4-0-dev` branch
+        run: |
+          sed -e '/rspec/d' -i Gemfile
+          cat << EOF > Gemfile.local
+            gem 'rspec', github: 'rspec/rspec', branch: '4-0-dev'
+            gem 'rspec-core', github: 'rspec/rspec-core', branch: '4-0-dev'
+            gem 'rspec-expectations', github: 'rspec/rspec-expectations', branch: '4-0-dev'
+            gem 'rspec-mocks', github: 'rspec/rspec-mocks', branch: '4-0-dev'
+            gem 'rspec-support', github: 'rspec/rspec-support', branch: '4-0-dev'
+          EOF
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 2.7
+          bundler-cache: true
+      - run: bundle exec rake spec

Gemfile

@@ -6,9 +6,7 @@ gemspec
 
 gem 'rack'
 gem 'rake'
-%w[rspec rspec-core rspec-expectations rspec-mocks rspec-support].each do |repo|
-  gem repo, github: "rspec/#{repo}", branch: '4-0-dev'
-end
+gem 'rspec', '~> 3.11'
 gem 'rubocop-performance', '~> 1.7'
 gem 'rubocop-rake', '~> 0.6'
 gem 'yard'