[guides] Add :guides namespace and :html and :kindle tasks to Rakefile

guides/Rakefile

@@ -1,11 +1,27 @@
-desc 'Generate guides (for authors), use ONLY=foo to process just "foo.textile"'
-task :generate_guides do
-  ENV["WARN_BROKEN_LINKS"] = "1" # authors can't disable this
-  ruby "rails_guides.rb"
-end
+namespace :guides do
+
+  desc 'Generate guides (for authors), use ONLY=foo to process just "foo.textile"'
+  task :generate => 'generate:html'
+
+  namespace :generate do
+
+    desc "Generate HTML guides"
+    task :html do
+      ENV["WARN_BROKEN_LINKS"] = "1" # authors can't disable this
+      ruby "rails_guides.rb"
+    end
+
+    desc "Generate .mobi file"
+    task :kindle do
+      ENV['KINDLE'] = '1'
+      Rake::Task['guides:generate:html'].invoke
+    end
+  end
+
+  # Validate guides -------------------------------------------------------------------------
+  desc 'Validate guides, use ONLY=foo to process just "foo.html"'
+  task :validate do
+    ruby "w3c_validator.rb"
+  end
 
-# Validate guides -------------------------------------------------------------------------
-desc 'Validate guides, use ONLY=foo to process just "foo.html"'
-task :validate_guides do
-  ruby "w3c_validator.rb"
 end