CI: do not test Rails Edge for CI workflows

- set an env var for CI workflows to denote CI workflow presence
- use a common Envfile helper to unshift Rails Edge onto the list of gem
  versions to test against
- update `active_record_pg`, `rails`, and `rails_prepend` to use the
  helper
- do not touch `active_record` at this time

.github/workflows/ci.yml

@@ -25,6 +25,7 @@ jobs:
         image: mysql:5.7
         env:
           MYSQL_ALLOW_EMPTY_PASSWORD: yes
+          CI_FOR_PR: true
         options: --health-cmd="mysqladmin ping" --health-interval=10s --health-timeout=5s --health-retries=3
         ports:
           - "3306:3306"
@@ -83,6 +84,7 @@ jobs:
         env:
           RUBY_VERSION: ${{ matrix.ruby-version }}
           RAILS_VERSION: ${{ env.rails }}
+          CI_FOR_PR: true
 
       - name: Run Unit Tests
         uses: nick-fields/retry@943e742917ac94714d2f408a0e8320f2d1fcafcd # tag v2.8.3
@@ -94,6 +96,7 @@ jobs:
           DB_PORT: ${{ job.services.mysql.ports[3306] }}
           VERBOSE_TEST_OUTPUT: true
           COVERAGE: true
+          CI_FOR_PR: true
 
       - name: Save coverage results
         uses: actions/upload-artifact@0b7f8abb1508181956e8e162db84b466c27e18ce # tag v3.1.2
@@ -253,6 +256,7 @@ jobs:
           POSTGRES_PASSWORD: password
           SERIALIZE: 1
           COVERAGE: true
+          CI_FOR_PR: true
 
       - name: Annotate errors
         if: ${{ failure() }}
@@ -306,6 +310,7 @@ jobs:
           VERBOSE_TEST_OUTPUT: true
           SERIALIZE: 1
           COVERAGE: true
+          CI_FOR_PR: true
 
       - name: Annotate errors
         if: ${{ failure() }}

test/multiverse/lib/multiverse/envfile.rb

@@ -133,6 +133,34 @@ def serialize?
       @serialize
     end
 
+    # add Rails Edge to the array of gem versions for testing,
+    # unless we're operating in a PR workflow context
+    def prepend_rails_edge(gem_version_array = [])
+      return if ci_for_pr?
+
+      # Unshift Rails Edge (representing the latest GitHub primary branch
+      # commit for https://github.com/rails/rails) onto the front of the
+      # gem version array. This produces the following line in the generated
+      # Gemfile file:
+      #
+      #   gem 'rails', github: 'rails'
+      #
+      # NOTE: Individually distributed Rails gems such as Active Record are each
+      #       contained within the same 'rails' GitHub repo. For now we are not
+      #       too concerned with cloning the entire Rails repo despite only
+      #       wanting to test one gem.
+      #
+      # NOTE: The Rails Edge version is not tested unless the Ruby version in
+      #       play is greater than or equal to (>=) the version number at the
+      #       end of the unshifted inner array
+      array.unshift(["github: 'rails'", 3.0])
+    end
+
+    # are we running in a CI context intended for PR approvals?
+    def ci_for_pr?
+      ENV.key?('CI_FOR_PR')
+    end
+
     private
 
     def last_supported_ruby_version?(last_supported_ruby_version)

test/multiverse/suites/active_record_pg/Envfile

@@ -12,7 +12,6 @@ end
 serialize!
 
 ACTIVERECORD_VERSIONS = [
-  ["github: 'rails'", 3.0], # Rails Edge
   [nil, 2.7],
   ['7.0.0', 2.7],
   ['6.1.0', 2.5],
@@ -22,6 +21,8 @@ ACTIVERECORD_VERSIONS = [
   ['5.0.0', 2.4, 2.7]
 ]
 
+prepend_rails_edge(ACTIVERECORD_VERSIONS)
+
 def gem_list(activerecord_version = nil)
   <<~RB
     gem 'activerecord'#{activerecord_version}

test/multiverse/suites/rails/Envfile

@@ -3,7 +3,6 @@
 # frozen_string_literal: true
 
 RAILS_VERSIONS = [
-  ["github: 'rails'", 3.0], # Rails Edge
   [nil, 2.7],
   ['7.0.4', 2.7],
   ['6.1.7', 2.5],
@@ -14,6 +13,8 @@ RAILS_VERSIONS = [
   ['4.2.11', 2.4, 2.4]
 ]
 
+prepend_rails_edge(RAILS_VERSIONS)
+
 def haml_rails(rails_version = nil)
   if rails_version && (
     rails_version.include?('4.0.13') ||

test/multiverse/suites/rails_prepend/Envfile

@@ -13,6 +13,8 @@ RAILS_VERSIONS = [
   ['4.2.0', 2.4, 2.4]
 ]
 
+prepend_rails_edge(RAILS_VERSIONS)
+
 def gem_list(rails_version = nil)
   # earlier thor errors, uncertain if they persist
   thor = "gem 'thor', '< 0.20.1'" if RUBY_PLATFORM == 'java' && rails_version && rails_version.include?('4')