Add CloudFormation UpdateStack call

lib/fog/aws/cloud_formation.rb

@@ -9,6 +9,7 @@ module Fog
 
       request_path 'fog/aws/requests/cloud_formation'
       request :create_stack
+      request :update_stack
       request :delete_stack
       request :describe_stack_events
       request :describe_stack_resources

lib/fog/aws/parsers/cloud_formation/update_stack.rb

@@ -0,0 +1,19 @@
+module Fog
+  module Parsers
+    module AWS
+      module CloudFormation
+
+        class UpdateStack < Fog::Parsers::Base
+
+          def end_element(name)
+            case name
+            when 'RequestId', 'StackId'
+              @response[name] = value
+            end
+          end
+
+        end
+      end
+    end
+  end
+end

lib/fog/aws/requests/cloud_formation/update_stack.rb

@@ -0,0 +1,62 @@
+module Fog
+  module AWS
+    class CloudFormation
+      class Real
+
+        require 'fog/aws/parsers/cloud_formation/update_stack'
+
+        # Update a stack
+        #
+        # ==== Parameters
+        # * stack_name<~String>: name of the stack to update
+        # * options<~Hash>:
+        #   * TemplateBody<~String>: structure containing the template body
+        #   or (one of the two Template parameters is required)
+        #   * TemplateURL<~String>: URL of file containing the template body
+        #   * Parameters<~Hash>: Hash of providers to supply to template
+        #   * Capabilities<~Array>: List of capabilties the stack is granted. Currently CAPABILITY_IAM
+        #     for allowing the creation of IAM resources
+        #
+        # ==== Returns
+        # * response<~Excon::Response>:
+        #   * body<~Hash>:
+        #     * 'StackId'<~String> - Id of the stack being updated
+        #
+        # ==== See Also
+        # http://docs.amazonwebservices.com/AWSCloudFormation/latest/APIReference/API_UpdateStack.html
+        #
+        def update_stack(stack_name, options = {})
+          params = {
+            'StackName' => stack_name,
+          }
+
+          if options['Parameters']
+            options['Parameters'].keys.each_with_index do |key, index|
+              index += 1 # params are 1-indexed
+              params.merge!({
+                "Parameters.member.#{index}.ParameterKey"   => key,
+                "Parameters.member.#{index}.ParameterValue" => options['Parameters'][key]
+              })
+            end
+          end
+
+          if options['TemplateBody']
+            params['TemplateBody'] = options['TemplateBody']
+          elsif options['TemplateURL']
+            params['TemplateURL'] = options['TemplateURL']
+          end
+
+          if options['Capabilities']
+            params.merge!(Fog::AWS.indexed_param("Capabilities.member", [*options['Capabilities']]))
+          end
+
+          request({
+            'Action'    => 'UpdateStack',
+            :parser     => Fog::Parsers::AWS::CloudFormation::UpdateStack.new
+          }.merge!(params))
+        end
+
+      end
+    end
+  end
+end

tests/aws/requests/cloud_formation/stack_tests.rb

@@ -18,6 +18,11 @@ Shindo.tests('AWS::CloudFormation | stack requests', ['aws', 'cloudformation'])
     'StackId'   => String
   }
 
+  @update_stack_format = {
+    'RequestId' => String,
+    'StackId'   => String
+  }
+
   @get_template_format = {
     'RequestId'     => String,
     'TemplateBody'  => String
@@ -103,6 +108,15 @@ Shindo.tests('AWS::CloudFormation | stack requests', ['aws', 'cloudformation'])
       ).body
     end
 
+    tests("update_stack('#{@stack_name}', 'TemplateURL' => '#{@template_url}', Parameters => {'KeyName' => 'cloudformation'})").formats(@update_stack_format) do
+      pending if Fog.mocking?
+      Fog::AWS[:cloud_formation].update_stack(
+        @stack_name,
+        'TemplateURL' => @template_url,
+        'Parameters'  => {'KeyName' => 'cloudformation'}
+      ).body
+    end
+
     tests("get_template('#{@stack_name})").formats(@get_template_format) do
       pending if Fog.mocking?
       Fog::AWS[:cloud_formation].get_template(@stack_name).body