Add absolute_image to account for custom registry

lib/mrsk/configuration.rb

@@ -24,6 +24,10 @@ class Mrsk::Configuration
     @version ||= ENV["VERSION"] || `git rev-parse HEAD`.strip
   end
 
+  def absolute_image
+    [ config.registry["server"], image ].compact.join("/")
+  end
+
   def image_with_version
     "#{image}:#{version}"
   end

test/configuration_test.rb

@@ -0,0 +1,16 @@
+require "test_helper"
+require "mrsk/configuration"
+
+class ConfigurationTest < ActiveSupport::TestCase
+  setup do
+    @config = { service: "app", image: "dhh/app", registry: { "username" => "dhh", "password" => "secret" } }
+  end
+
+  test "absolute image" do
+    configuration = Mrsk::Configuration.new(@config)
+    assert_equal "dhh/app", configuration.absolute_image
+
+    configuration = Mrsk::Configuration.new(@config.tap { |c| c[:registry].merge!({ "server" => "ghcr.io" }) })
+    assert_equal "ghcr.io/dhh/app", configuration.absolute_image
+  end
+end