Add support for on-disk file streaming.

lib/gollum/app.rb

@@ -403,9 +403,13 @@ module Precious
         @bar_side  = wiki.bar_side
 
         mustache :page
-      elsif file = wiki.file(fullpath)
-        content_type file.mime_type
-        file.raw_data
+      elsif file = wiki.file(fullpath, wiki.ref, true)
+        if file.on_disk?
+          send_file file.on_disk_path, :disposition => 'inline'
+        else
+          content_type file.mime_type
+          file.raw_data
+        end
       else
         page_path = [path, name].compact.join('/')
         redirect to("/create/#{clean_url(encodeURIComponent(page_path))}")

test/test_app.rb

@@ -578,6 +578,12 @@ context "Frontend with lotr" do
     assert_match /Bilbo Baggins/, last_response.body
   end
 
+  test "streaming files to browser" do
+    get "/Data.csv"
+    assert last_response.ok?
+    assert last_response.headers.include? 'Content-Disposition'
+  end
+
   # base path requires 'map' in a config.ru to work correctly.
   test "create pages within sub-directories using base path" do
     Precious::App.set(:wiki_options, { :base_path => 'wiki' })