Use Base class for default config assignment

lib/mrsk/commands.rb

@@ -1,4 +1,11 @@
 module Mrsk::Commands
+  class Base
+    attr_accessor :config
+
+    def initialize(config)
+      @config = config
+    end
+  end
 end
 
 require "mrsk/commands/app"

lib/mrsk/commands/app.rb

@@ -1,10 +1,4 @@
-class Mrsk::Commands::App
-  attr_accessor :config
-
-  def initialize(config)
-    @config = config
-  end
-
+class Mrsk::Commands::App < Mrsk::Commands::Base
   def push
     # TODO: Run 'docker buildx create --use' when needed
     "docker buildx build --push --platform=linux/amd64,linux/arm64 -t #{config.image_with_version} ."

lib/mrsk/commands/registry.rb

@@ -1,4 +1,4 @@
-class Mrsk::Commands::Registry
+class Mrsk::Commands::Registry < Mrsk::Commands::Base
   def login
     if (user = ENV["DOCKER_USER"]).present? && (password = ENV["DOCKER_PASSWORD"]).present?
       # FIXME: Find a way to hide PW so it's not shown on terminal

lib/mrsk/commands/traefik.rb

@@ -1,4 +1,4 @@
-class Mrsk::Commands::Traefik
+class Mrsk::Commands::Traefik < Mrsk::Commands::Base
   def start
     "docker run --name traefik " + 
       "--rm -d " +