post versions: fix undo action.

app/controllers/post_versions_controller.rb

@@ -24,7 +24,7 @@ class PostVersionsController < ApplicationController
     @post_version = authorize PostVersion.find(params[:id])
     @post_version.undo!
 
-    respond_with(@post_version)
+    respond_with(@post_version, location: post_versions_path(search: { post_id: @post_version.post_id }))
   end
 
   private

app/views/post_versions/_listing.html.erb

@@ -31,7 +31,7 @@
         </div>
       <% end %>
       <% t.column do |post_version| %>
-        <% if policy(post_version).can_undo? %>
+        <% if policy(post_version).undo? %>
           <%= link_to "Undo", undo_post_version_path(post_version), method: :put, remote: true, class: "post-version-undo-link" %>
         <% end %>
         <% if listing_type(:post_id) == :revert && policy(post_version.post).revert? %>

test/functional/post_versions_controller_test.rb

@@ -5,7 +5,7 @@ class PostVersionsControllerTest < ActionDispatch::IntegrationTest
     @user = create(:user)
 
     as(@user) do
-      @post = create(:post, tag_string: "tagme", rating: "s")
+      @post = create(:post, tag_string: "tagme", rating: "s", source: "blah")
       travel(2.hours) { @post.update(tag_string: "1 2", source: "xxx") }
       travel(4.hours) { @post.update(tag_string: "2 3", rating: "e") }
       @post2 = create(:post)
@@ -45,10 +45,11 @@ class PostVersionsControllerTest < ActionDispatch::IntegrationTest
 
     context "undo action" do
       should "undo the edit" do
-        put_auth undo_post_version_path(@post.versions.first), @user
-        assert_response :success
-        assert_equal("s", @post.reload.rating)
-        assert_equal("tagme", @post.reload.tag_string)
+        put_auth undo_post_version_path(@post.versions.second), @user
+        assert_response :redirect
+        assert_equal("e", @post.reload.rating)
+        assert_equal("3 tagme", @post.tag_string)
+        assert_equal("blah", @post.source)
       end
 
       should "not allow non-members to undo edits" do