Add support for fog streaming uploads

Fog supports streaming uploads if passed a File object.
Added SanitizedFile#to_file method that returns a File object.
This works for file system based SanitizedFile (File, Tempfile, Hash, etc)
StringIO must still be read into memory before being passed to fog.

lib/carrierwave/sanitized_file.rb

@@ -216,6 +216,17 @@ def delete
       FileUtils.rm(self.path) if exists?
     end
 
+    ##
+    # Returns a File object, or nil if it does not exist.
+    #
+    # === Returns
+    #
+    # [File] a File object representing the SanitizedFile
+    #
+    def to_file
+      File.open(@file) if exists?
+    end
+
     ##
     # Returns the content type of the file.
     #

lib/carrierwave/storage/fog.rb

@@ -227,7 +227,7 @@ def size
         def store(new_file)
           @content_type ||= new_file.content_type
           @file = directory.files.create({
-            :body         => new_file.read,
+            :body         => new_file.exists? ? new_file.to_file : new_file.read,
             :content_type => @content_type,
             :key          => path,
             :public       => @uploader.fog_public

spec/sanitized_file_spec.rb

@@ -383,6 +383,20 @@
         File.exists?(@sanitized_file.path).should be_false
       end
     end
+
+    describe '#to_file' do
+      it "should return a File object" do
+        @sanitized_file.to_file.should be_a(File)
+      end
+
+      it "should have the same path as the SanitizedFile" do
+        @sanitized_file.to_file.path.should == @sanitized_file.path
+      end
+
+      it "should have the same contents as the SantizedFile" do
+        @sanitized_file.to_file.read.should == @sanitized_file.read
+      end
+    end
   end
 
   describe "with a valid Hash" do
@@ -470,6 +484,12 @@
       end
     end
 
+    describe '#to_file' do
+      it "should be nil" do
+        @sanitized_file.to_file.should be_nil
+      end
+    end
+
   end
 
   describe "with a valid File object" do
@@ -614,6 +634,12 @@
         running { @empty.delete }.should_not raise_error
       end
     end
+
+    describe '#to_file' do
+      it "should be nil" do
+        @empty.to_file.should be_nil
+      end
+    end
   end
 
   describe "that is an empty string" do
@@ -680,6 +706,12 @@
         running { @empty.delete }.should_not raise_error
       end
     end
+
+    describe '#to_file' do
+      it "should be nil" do
+        @empty.to_file.should be_nil
+      end
+    end
   end
 
 end