add Ruby version to Gemfile.lock

Signed-off-by: David Morhovich <dmorhovich@pivotal.io>

lib/bundler/definition.rb

@@ -307,6 +307,11 @@ def to_lock
         out << "  #{p}\n"
       end
 
+      if ruby_version
+        out << "\nRUBY VERSION\n"
+        out << "  #{Bundler.ruby_version}\n"
+      end
+
       out << "\n"
       out << "DEPENDENCIES\n"
 

spec/lock/lockfile_spec.rb

@@ -1124,6 +1124,33 @@
     G
   end
 
+  it "captues the Ruby version in the lockfile", :focus do
+    install_gemfile <<-G
+      source "file://#{gem_repo1}"
+      ruby '#{RUBY_VERSION}'
+      gem "rack", "> 0.9", "< 1.0"
+    G
+
+    lockfile_should_be <<-G
+      GEM
+        remote: file:#{gem_repo1}/
+        specs:
+          rack (0.9.1)
+
+      PLATFORMS
+        ruby
+
+      RUBY VERSION
+        ruby #{RUBY_VERSION}p#{RUBY_PATCHLEVEL}
+
+      DEPENDENCIES
+        rack (> 0.9, < 1.0)
+
+      BUNDLED WITH
+         #{Bundler::VERSION}
+    G
+  end
+
   # Some versions of the Bundler 1.1 RC series introduced corrupted
   # lockfiles. There were two major problems:
   #