add basic user revert functionality

app/views/post_versions/index.html.erb

@@ -7,6 +7,10 @@
     <% else %>
       <%= render "listing", :post_versions => @post_versions %>
 
+      <% if params[:lr] && CurrentUser.is_janitor? %>
+        <p><%= link_to "Revert this user's changes", new_user_revert_path(:user_id => params[:lr]) %></p>
+      <% end %>
+
       <%= numbered_paginator(@post_versions) %>
     <% end %>
   </div>

app/views/user_reverts/new.html.erb

@@ -0,0 +1,19 @@
+<div id="c-users">
+  <div id="a-new">
+    <h1>Revert Changes</h1>
+
+    <p>You are about to revert all changes made by <%= link_to_user @user %>. Continue?</p>
+
+    <%= form_tag(user_revert_path) do %>
+      <%= hidden_field_tag :user_id, params[:user_id] %>
+
+      <%= submit_tag "Yes" %>
+    <% end %>
+  </div>
+</div>
+
+<%= render "users/secondary_links" %>
+
+<% content_for(:page_title) do %>
+  User Revert - <%= Danbooru.config.app_name %>
+<% end %>

app/views/users/_statistics.html.erb

@@ -56,7 +56,12 @@
 
       <tr>
         <th>Post Changes</th>
-        <td><%= presenter.post_version_count(self) %></td>
+        <td>
+          <%= presenter.post_version_count(self) %>
+          <% if CurrentUser.is_janitor? %>
+            [<%= link_to "revert all", new_user_revert_path(user_id: user.id) %>]
+          <% end %>
+        </td>
       </tr>
 
       <tr>