[bundler/bundler] Add required_ruby_version to gemspec template

https://github.com/bundler/bundler/commit/f47421f92d

lib/bundler/templates/newgem/newgem.gemspec.tt

@@ -12,6 +12,7 @@ Gem::Specification.new do |spec|
 <%- if config[:mit] -%>
   spec.license       = "MIT"
 <%- end -%>
+  spec.required_ruby_version = Gem::Requirement.new(">= 2.3.0")
 
   spec.metadata["allowed_push_host"] = "TODO: Set to 'http://mygemserver.com'"
 

spec/bundler/commands/newgem_spec.rb

@@ -274,6 +274,12 @@ RSpec.describe "bundle gem" do
         to match(/mygemserver\.com/)
     end
 
+    it "sets a minimum ruby version" do
+      bundler_gemspec = Bundler::GemHelper.new(File.expand_path("../..", __dir__)).gemspec
+
+      expect(bundler_gemspec.required_ruby_version).to eq(generated_gemspec.required_ruby_version)
+    end
+
     it "requires the version file" do
       expect(bundled_app("test_gem/lib/test_gem.rb").read).to match(%r{require "test_gem/version"})
     end