Include edge Rails in the build matrix

Highlighting an incompatibility with the new implementation of
`[ActiveSupport::OrderedOptions#dig]`.

[^1]: 5c15b586aa

.github/workflows/ci.yml

@@ -8,12 +8,15 @@ jobs:
           - "2.7"
           - "3.1"
           - "3.2"
+        gemfile:
+          - Gemfile
+          - gemfiles/rails_edge.gemfile
         continue-on-error: [false]
-
     name: ${{ format('Tests (Ruby {0})', matrix.ruby-version) }}
     runs-on: ubuntu-latest
     continue-on-error: ${{ matrix.continue-on-error }}
-
+    env:
+      BUNDLE_GEMFILE: ${{ github.workspace }}/${{ matrix.gemfile }}
     steps:
       - uses: actions/checkout@v2
 

.gitignore

@@ -1,4 +1,5 @@
 .byebug_history
 *.gem
 coverage/*
-.DS_Store
+.DS_Store
+gemfiles/*.lock

Gemfile

@@ -2,7 +2,3 @@ source 'https://rubygems.org'
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
 gemspec
-
-gem "debug"
-gem "mocha"
-gem "railties"

gemfiles/rails_edge.gemfile

@@ -0,0 +1,9 @@
+source 'https://rubygems.org'
+git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
+git "https://github.com/rails/rails.git" do
+  gem "railties"
+  gem "activesupport"
+end
+
+gemspec path: "../"

mrsk.gemspec

@@ -19,4 +19,8 @@ Gem::Specification.new do |spec|
   spec.add_dependency "zeitwerk", "~> 2.5"
   spec.add_dependency "ed25519", "~> 1.2"
   spec.add_dependency "bcrypt_pbkdf", "~> 1.0"
+
+  spec.add_development_dependency "debug"
+  spec.add_development_dependency "mocha"
+  spec.add_development_dependency "railties"
 end