added comment button to posts

app/models/ability.rb

@@ -20,12 +20,16 @@ class Ability
       can :update, ScientificName
       can :destroy, ScientificName
 
-      # anyone can create a post, but only the author can edit/destroy
-      # it.
+      # anyone can create a post, or comment on a post,
+      # but only the author can edit/destroy it.
       can :create, Post
       can :update, Post, :author_id => member.id
       can :destroy, Post, :author_id => member.id
 
+      can :create, Comment
+      can :update, Comment, :author_id => member.id
+      can :destroy, Comment, :author_id => member.id
+
       # same deal for gardens and plantings
       can :create, Garden
       can :update, Garden, :owner_id => member.id

app/views/posts/_single.html.haml

@@ -24,3 +24,7 @@
             - if can? :destroy, post
               = link_to 'Delete', post, method: :delete, |
                 data: { confirm: 'Are you sure?' }, :class => 'btn'
+
+        - if can? :create, Comment
+          .post-actions
+            =link_to 'Comment', new_comment_path(), :class => 'btn'

spec/views/posts/show.html.haml_spec.rb

@@ -34,4 +34,19 @@ describe "posts/show" do
     rendered.should_not match(/a href="http:\/\/evil.com"/)
   end
 
+  context "signed in" do
+    before(:each) do
+      sign_in @author
+      controller.stub(:current_user) { @author }
+      @post = assign(:post,
+        FactoryGirl.create(:post, :author => @author))
+      render
+    end
+
+    it 'shows a comment button' do
+      assert_select "a[href=#{new_comment_path}]", "Comment"
+    end
+
+  end
+
 end