Use symlinks for multiple Gemfiles

Author: rosston

example/Gemfile

@@ -1,4 +1,20 @@
 source "https://rubygems.org"
 
-gem "rails"
-eval_gemfile "Gemfile.common"
+def rails_version
+  current_gemfile = File.basename(__FILE__)
+
+  {
+    "Gemfile" => nil,
+    "Gemfile_rails71" => "~> 7.1.3"
+  }.fetch(current_gemfile)
+end
+
+gem "rails", rails_version
+gem "sqlite3"
+gem "puma"
+gem "webpacker"
+gem "bootsnap", require: false
+
+group :development, :test do
+  gem "cypress-rails", path: ".."
+end

example/Gemfile.rails71

@@ -0,0 +1 @@
+Gemfile

example/Gemfile_rails71

@@ -205,7 +205,7 @@ DEPENDENCIES
   bootsnap
   cypress-rails!
   puma
-  rails (~> 7.1, < 7.2)
+  rails (~> 7.1.3)
   sqlite3
   webpacker
 

example/Gemfile.rails71.lock renamed to example/Gemfile_rails71.lock

@@ -1,7 +1,7 @@
 # README
 
-The example app has multiple Gemfiles to be able to test against different
-dependency versions (so far just Rails).
+The example app has multiple, symlinked Gemfiles to be able to test against
+different dependency versions (so far just Rails).
 
 For the latest version of Rails, you can just use all the default `bundle`
 commands:
@@ -11,13 +11,9 @@ bundle exec rake cypress:run
 ```
 
 For previous version(s) of Rails, you need to specify the Gemfile to use. So
-for `Gemfile.rails71` (which uses Rails 7.1), you'll need to include an env var
+for `Gemfile_rails71` (which uses Rails 7.1), you'll need to include an env var
 when you use `bundle` commands:
 ```
-BUNDLE_GEMFILE=Gemfile.rails71 bundle
-BUNDLE_GEMFILE=Gemfile.rails71 bundle exec rake cypress:run
+BUNDLE_GEMFILE=Gemfile_rails71 bundle
+BUNDLE_GEMFILE=Gemfile_rails71 bundle exec rake cypress:run
 ```
-
-If you're adding/changing a dependency that won't differ between the multiple
-Gemfiles, then you can make that change in `Gemfile.common` so that it gets
-picked up in all the Gemfiles.