title: How do I prevent multiple RKResponseDescriptors from matching?
body: <p>I am using RestKit 0.20.0rc1 in an app that uses 2 entities:</p>
  
  <ol>
  <li>A "note" (NoteClass).</li>
  <li>A "set" (SetClass), which contains a collection of notes.</li>
  </ol>
  
  <p>I have the following 2 response descriptors (among others):</p>
  
  <pre><code>// GET /sets/:setID/notes
  // Get a set's notes. Response looks like this:
  //   {"notes": [ (array of NoteClass dictionaries) ],
  //               ...more stuff...
  //   }
  RKResponseDescriptor *noteResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:[NoteClass rkEntityMapping]
                                                               pathPattern:@"/sets/:setID/notes"
                                                                   keyPath:@"notes"
                                                               statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
  [objectManager addResponseDescriptor:noteResponseDescriptor];
  
  // GET /sets/:setID
  // Get information about a set. Response looks like this:
  //   {"name": "My Set",
  //    "numNotes": 3,
  //    ...more stuff...
  //   }
  RKResponseDescriptor *setResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:[SetClass rkEntityMapping]
                                                               pathPattern:@"/sets/:setID"
                                                                   keyPath:nil
                                                               statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
  [objectManager addResponseDescriptor:setResponseDescriptor];
  </code></pre>
  
  <p>When I request "/sets/:setID/notes", the noteResponseDescriptor matches (expected). However, the setResponseDescriptor also matches (unexpected). I believe this is because the response descriptor's path pattern matches the substring "/sets/:setID", and because key path is nil. As a result, when I make the request, the RKMappingResult I get back contains an array of NoteClass objects (expected) and a single empty SetClass object (unexpected).</p>
  
  <p>How do I prevent the setResponseDescriptor from matching this notes endpoint? I can't add a key path to the setResponseDescriptor (yet), so my preference is for a solution that allows me to say something like "match /sets/:setID$", where "$" designates the end of the URL.</p>