Making it easier to get pre-signed head requests

Very similar to get_url. https://github.com/fog/fog-aws/issues/47

lib/fog/aws/models/storage/files.rb

@@ -92,6 +92,11 @@ module Fog
           service.get_object_https_url(directory.key, key, expires, options)
         end
 
+        def head_url(key, expires, options = {})
+          requires :directory
+          service.head_object_url(directory.key, key, expires, options)
+        end
+
         def head(key, options = {})
           requires :directory
           data = service.head_object(directory.key, key, options)

lib/fog/aws/requests/storage/head_object_url.rb

@@ -0,0 +1,40 @@
+module Fog
+  module Storage
+    class AWS
+      module HeadObjectUrl
+        def head_object_url(bucket_name, object_name, expires, options = {})
+          unless bucket_name
+            raise ArgumentError.new('bucket_name is required')
+          end
+          unless object_name
+            raise ArgumentError.new('object_name is required')
+          end
+          signed_url(options.merge({
+            :bucket_name => bucket_name,
+            :object_name => object_name,
+            :method => 'HEAD'
+          }), expires)
+        end
+      end
+
+      class Real
+        # An expiring head request url from S3
+        #
+        # @param bucket_name [String] Name of bucket containing object
+        # @param object_name [String] Name of object to get expiring url for
+        # @param expires [Time] An expiry time for this url
+        #
+        # @return [Excon::Response] response:
+        #   * body [String] - url for object
+        #
+        # @see http://docs.amazonwebservices.com/AmazonS3/latest/dev/S3_QSAuth.html
+
+        include HeadObjectUrl
+      end
+
+      class Mock # :nodoc:all
+        include HeadObjectUrl
+      end
+    end
+  end
+end

lib/fog/aws/storage.rb

@@ -88,6 +88,7 @@ module Fog
       request :get_service
       request :head_bucket
       request :head_object
+      request :head_object_url
       request :initiate_multipart_upload
       request :list_multipart_uploads
       request :list_parts

tests/requests/storage/object_tests.rb

@@ -118,6 +118,12 @@ Shindo.tests('AWS::Storage | object requests', ['aws']) do
       (object_url =~ /http:\/\/#{Regexp.quote(@directory.identity)}\.s3\.amazonaws\.com\/fog_object/) != nil
     end
 
+    tests("#head_object_url('#{@directory.identity}', 'fog_object', expiration timestamp)").returns(true) do
+      object_url = Fog::Storage[:aws].head_object_url(@directory.identity, 'fog_object', (Time.now + 60))
+      puts object_url
+      (object_url =~ /https:\/\/#{Regexp.quote(@directory.identity)}\.s3\.amazonaws\.com\/fog_object/) != nil
+    end
+
     tests("delete_multiple_objects('#{@directory.identity}', ['fog_object', 'fog_other_object'])").formats(@multiple_delete_format) do
       Fog::Storage[:aws].delete_multiple_objects(@directory.identity, ['fog_object', 'fog_other_object']).body
     end