Check for env.rb via ENV_LOADED instead of respond_to?(:require)

The rubygem 'polyglot', which is depended on by Cucumber via Treetop,
redefines the Kernel#require method, making it public instead of
private. This is pretty horrible. Libraries should not break the
behaviour of the stdlib. :(

This commit implements a workaround for that particular issue, with
a test that does the same thing polyglot does.

Closes rubygems#287

lib/bundler.rb

@@ -87,12 +87,12 @@ def gem_setup(*groups)
         exit!
       end
     end
-    alias setup gem_setup unless Bundler.respond_to?(:setup)
+    alias setup gem_setup unless defined?(Bundler::ENV_LOADED)
 
     def gem_require(*groups)
       setup(*groups).require(*groups)
     end
-    alias require gem_require unless Bundler.respond_to?(:require)
+    alias require gem_require unless defined?(Bundler::ENV_LOADED)
 
     def load
       @load ||= begin

lib/bundler/templates/environment.erb

@@ -6,6 +6,7 @@ require 'yaml'
 <%= shared_helpers %>
 
 module Bundler
+  ENV_LOADED   = true
   LOCKED_BY    = '<%= Bundler::VERSION %>'
   FINGERPRINT  = <%= gemfile_fingerprint.inspect %>
   HOME         = '<%= Bundler.home %>'

spec/runtime/environment_rb_spec.rb

@@ -218,7 +218,27 @@ def Bundler.require(path)
       bundle :lock
 
       bundle %|exec ruby -e "require 'bundler'; Bundler.setup"|
-      err.should == ""
+      err.should be_empty
+    end
+
+    it "handles polyglot making Kernel#require public :(" do
+      install_gemfile <<-G
+        source "file://#{gem_repo1}"
+        gem "rack"
+      G
+
+      ruby <<-RUBY
+        require 'rubygems'
+        module Kernel
+          alias polyglot_original_require require
+          def require(*a, &b)
+            polyglot_original_require(*a, &b)
+          end
+        end
+        require 'bundler'
+        Bundler.require(:foo, :bar)
+      RUBY
+      err.should be_empty
     end
   end
 end

spec/support/builders.rb

@@ -124,11 +124,11 @@ def build_repo1
         end
 
         build_gem "yard" do |s|
-          s.write "lib/yard.rb", <<-Y
+          s.write "lib/yard.rb", <<-RUBY
             Gem.source_index.find_name('').each do |gem|
               require gem.name
             end
-          Y
+          RUBY
         end
 
         # Test comlicated gem dependencies for install