Properly refresh last build link on repos list

value change. Since {{action}} is also not a bound helper, I need some
structure that I can put into {{with}} helper

assets/scripts/app/models/repo.coffee

@@ -12,6 +12,14 @@ require 'travis/model'
 
   lastBuild: DS.belongsTo('Travis.Build')
 
+  lastBuildHash: (->
+    {
+      id: @get('lastBuildId')
+      number: @get('lastBuildNumber')
+      repo: this
+    }
+  ).property('lastBuildId', 'lastBuildNumber')
+
   allBuilds: (->
     allBuilds = DS.RecordArray.create
       type: Travis.Build

assets/scripts/app/templates/repos/list.hbs

@@ -13,8 +13,9 @@
           <a {{action showRepo this href=true}} class="slug">{{slug}}</a>
         {{/if}}
       </div>
-      {{#if lastBuildId}}
-        <a {{action showBuild this lastBuildId href=true}} class="last_build">{{lastBuildNumber}}</a>
+      {{#with lastBuildHash}}
+        {{#if id}}
+        <a {{action showBuild repo id href=true}} class="last_build">{{number}}</a>
       {{/if}}
 
       <p class="summary">