Pool versions diff: Use diff builder to highlight description changes

- Add highlights for name changes
- Separate and name the sections

app/helpers/pool_versions_helper.rb

@@ -18,4 +18,9 @@ module PoolVersionsHelper
     status += ["Deactivated"] if !cur.is_active? && prev.is_active?
     status.join(" ")
   end
-end
+
+  def pool_page_diff(pool_version, other_version)
+    pattern = Regexp.new('(?:<.+?>)|(?:\w+)|(?:[ \t]+)|(?:\r?\n)|(?:.+?)')
+    DiffBuilder.new(other_version.description, pool_version.description, pattern).build
+  end
+end

app/javascript/src/styles/specific/pool_versions.scss

@@ -0,0 +1,13 @@
+div#c-pool-versions {
+  #a-diff {
+    del {
+      background: var(--wiki-page-versions-diff-del-background);
+      text-decoration: none;
+    }
+
+    ins {
+      background: var(--wiki-page-versions-diff-ins-background);
+      text-decoration: none;
+    }
+  }
+}

app/views/pool_versions/diff.html.erb

@@ -2,16 +2,33 @@
   <div id="a-diff">
     <h1>Pool Version Comparison: <%= @pool_version.name %></h1>
 
-    <ul>
-      <li>
-        <strong>Posts</strong>:
-        <%= render "pool_versions/diff", diff: @pool_version.build_diff(@other_version) %>
-      </li>
-      <% if @other_version %>
-        <li><strong>Old Desc</strong>: <%= @other_version.description %></li>
-      <% end %>
-      <li><strong>New Desc</strong>: <%= @pool_version.description %></li>
-    </ul>
+    <% if @other_version.present? %>
+      <p>Showing differences between <%= compact_time @pool_version.updated_at %> (<%= link_to_user @pool_version.updater %>) and <%= compact_time @other_version.updated_at %> (<%= link_to_user @other_version.updater %>)</p>
+      <div>
+        <h2>Name:</h2>
+        <p>
+          <% if @pool_version.name != @other_version.name %>
+            <del><%= @other_version.name %></del> -> <ins><%= @pool_version.name %></ins>
+          <% else %>
+            <%= @pool_version.name %>
+          <% end %>
+        </p>
+      </div>
+      <div>
+        <h2>Posts:</h2>
+        <p><%= render "pool_versions/diff", diff: @pool_version.build_diff(@other_version) %></p>
+      </div>
+      <div>
+        <h2>Description:</h2>
+        <p>
+          <% if @pool_version.description != @other_version.description %>
+            <%= pool_page_diff(@pool_version, @other_version) %>
+          <% else %>
+            <i>Unchanged.</i>
+          <% end %>
+        </p>
+      </div>
+    <% end %>
   </div>
 </div>