[filesystem storage] Create :override_file_permissions option

This allows you to set custom file permissions on files created by
Paperclip.  Set the :override_file_permissions option to the octal file
permission you want - 0666 is the default. If you set
:override_file_permissions to false, then we will skip the explicit
chmod entirely. This makes filesystem storage a bit friendlier to filesystems
that don't support unix file permissions.

lib/paperclip/storage/filesystem.rb

@@ -35,7 +35,10 @@ module Paperclip
               new_file.write(chunk)
             end
           end
-          FileUtils.chmod(0666&~File.umask, path(style_name))
+          unless @options[:override_file_permissions] == false
+            resolved_chmod = (@options[:override_file_permissions]&~0111) || (0666&~File.umask)
+            FileUtils.chmod( resolved_chmod, path(style_name) )
+          end
           file.rewind
         end
 

test/integration_test.rb

@@ -293,6 +293,35 @@ class IntegrationTest < Test::Unit::TestCase
     end
   end
 
+  [0666,0664,0640].each do |perms|
+    context "when the perms are #{perms}" do
+      setup do
+        rebuild_model :override_file_permissions => perms
+        @dummy = Dummy.new
+        @file  = File.new(fixture_file("5k.png"), 'rb')
+      end
+
+      teardown do
+        @file.close
+      end
+
+      should "respect the current perms" do
+        @dummy.avatar = @file
+        @dummy.save
+        assert_equal perms, File.stat(@dummy.avatar.path).mode & 0777
+      end
+    end
+  end
+
+  should "skip chmod operation, when override_file_permissions is set to false (e.g. useful when using CIFS mounts)" do
+    FileUtils.expects(:chmod).never
+
+    rebuild_model :override_file_permissions => false
+    dummy = Dummy.create!
+    dummy.avatar = @file
+    dummy.save
+  end
+
   context "A model with a filesystem attachment" do
     setup do
       rebuild_model :styles => { :large => "300x300>",