rel nofollow, on by default to protect forums from spam etc. we should consider lifting it at high trust by default.

spec/components/pretty_text_spec.rb

@@ -75,6 +75,24 @@ test
         .should == "<pre><code>```\nhello\n```\n</code></pre>"
     end
   end
+  
+  describe "rel nofollow" do
+    before do 
+      SiteSetting.stubs(:add_rel_nofollow_to_user_content).returns(true)
+    end
+
+    it "should inject nofollow in all user provided links" do 
+      PrettyText.cook('<a href="http://cnn.com">cnn</a>').should =~ /nofollow/
+    end
+    
+    it "should not inject nofollow in all local links" do 
+      (PrettyText.cook("<a href='#{Discourse.base_url}/test.html'>cnn</a>") !~ /nofollow/).should be_true  
+    end
+    
+    it "should not inject nofollow in all subdomain links" do 
+      (PrettyText.cook("<a href='#{Discourse.base_url.sub('http://', 'http://bla.')}/test.html'>cnn</a>") !~ /nofollow/).should be_true  
+    end
+  end
 
   describe "Excerpt" do 
     it "should preserve links" do 
@@ -130,6 +148,7 @@ test
     end
   end
 
+
   describe "apply cdn" do 
     it "should detect bare links to images and apply a CDN" do
       PrettyText.apply_cdn("<a href='/hello.png'>hello</a><img src='/a.jpeg'>","http://a.com").should ==