cache command no longer prunes gems built with older rubygems versions

lib/bundler/cli.rb

@@ -72,6 +72,7 @@ def check
     method_option "relock",  :type => :boolean, :banner => "Unlock, install the gems, and relock."
     method_option "disable-shared-gems", :type => :boolean, :banner => "Do not use any shared gems, such as the system gem repository."
     method_option "gemfile", :type => :string, :banner => "Use the specified gemfile instead of Gemfile"
+    method_option "no-prune",  :type => :boolean, :banner => "Don't remove stale gems from the cache."
     def install(path = nil)
       opts = options.dup
       opts[:without] ||= []
@@ -91,11 +92,11 @@ def install(path = nil)
         raise GemfileChanged, "You changed your Gemfile after locking. " +
           "Please run `bundle install --relock`."
       end
-      Bundler.ui.confirm "Your bundle is complete! " +
-        "Use `bundle show [gemname]` to see where a bundled gem is installed."
 
       lock if options[:relock]
       cache if Bundler.root.join("vendor/cache").exist?
+      Bundler.ui.confirm "Your bundle is complete! " +
+        "Use `bundle show [gemname]` to see where a bundled gem is installed."
     rescue GemNotFound => e
       if Bundler.definition.sources.empty?
         Bundler.ui.warn "Your Gemfile doesn't have any sources. You can add one with a line like 'source :gemcutter'"

spec/cache/gems_spec.rb

@@ -115,6 +115,17 @@
       cached_gem("actionpack-2.3.2").should_not exist
       cached_gem("activesupport-2.3.2").should_not exist
     end
+
+    it "doesn't remove gems with mismatched :rubygems_version or :date" do
+      cached_gem("rack-1.0.0").rmtree
+      build_gem "rack", "1.0.0",
+        :path => bundled_app('vendor/cache'),
+        :rubygems_version => "1.3.2"
+      simulate_new_machine
+
+      bundle :install
+      cached_gem("rack-1.0.0").should exist
+    end
   end
 
 end

spec/support/builders.rb

@@ -369,6 +369,13 @@ def add_c_extension
 
       def _build(options)
         path = options[:path] || _default_path
+
+        if options[:rubygems_version]
+          @spec.rubygems_version = options[:rubygems_version]
+          def @spec.mark_version; end
+          def @spec.validate; end
+        end
+
         case options[:gemspec]
         when false
           # do nothing
@@ -381,6 +388,7 @@ def _build(options)
         unless options[:no_default]
           @files = _default_files.merge(@files)
         end
+
         @files.each do |file, source|
           file = Pathname.new(path).join(file)
           FileUtils.mkdir_p(file.dirname)