static files mtime liquid should return a Time obj

lib/jekyll/static_file.rb

@@ -18,7 +18,7 @@ module Jekyll
       @name = name
       @collection = collection
       @relative_path = File.join(*[@dir, @name].compact)
-      @extname = File.extname(@relative_path)
+      @extname = File.extname(@name)
     end
 
     # Returns source file path.
@@ -43,9 +43,13 @@ module Jekyll
       end
     end
 
+    def modified_time
+      @modified_time ||= File.stat(path).mtime
+    end
+
     # Returns last modification time for this file.
     def mtime
-      File.stat(path).mtime.to_i
+      modified_time.to_i
     end
 
     # Is source path modified?
@@ -91,9 +95,9 @@ module Jekyll
 
     def to_liquid
       {
-        "path"          => File.join("", relative_path),
-        "modified_time" => mtime.to_s,
-        "extname"       => extname
+        "extname"       => extname,
+        "modified_time" => modified_time,
+        "path"          => File.join("", relative_path)
       }
     end
   end

site/_data/docs.yml

@@ -13,6 +13,7 @@
   - posts
   - drafts
   - pages
+  - static-files
   - variables
   - collections
   - datafiles

site/_docs/static_files.md

@@ -0,0 +1,52 @@
+---
+layout: docs
+title: Static Files
+permalink: /docs/static-files/
+---
+
+In addition to renderable and convertible content, we also have **static
+files**.
+
+A static file is a file that does not contain any YAML front matter. These
+include images, PDFs, and other un-rendered content.
+
+They're accessible in Liquid via `site.static_files` and contain the
+following metadata:
+
+<div class="mobile-side-scroller">
+<table>
+  <thead>
+    <tr>
+      <th>Variable</th>
+      <th>Description</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td><p><code>file.path</code></p></td>
+      <td><p>
+
+        The relative path to the file.
+
+      </p></td>
+    </tr>
+    <tr>
+      <td><p><code>file.modified_time</code></p></td>
+      <td><p>
+
+        The `Time` the file was last modified.
+
+      </p></td>
+    </tr>
+    <tr>
+      <td><p><code>file.extname</code></p></td>
+      <td><p>
+
+        The extension name for the file, e.g.
+        <code>.jpg</code> for <code>image.jpg</code>
+
+      </p></td>
+    </tr>
+  </tbody>
+</table>
+</div>