Create missing buildx builder if missing automatically

lib/mrsk/commands/app.rb

@@ -1,7 +1,5 @@
 class Mrsk::Commands::App < Mrsk::Commands::Base
   def push
-    # TODO: Run 'docker buildx create --use' when needed
-    # TODO: Make multiarch an option so Linux users can enjoy speedier builds
     docker :buildx, :build, "--push", "--platform linux/amd64,linux/arm64", "-t", config.absolute_image, "."
   end
 
@@ -64,6 +62,10 @@ class Mrsk::Commands::App < Mrsk::Commands::Base
     docker :image, :prune, "-a", "-f", *service_filter
   end
 
+  def create_new_builder
+    docker :buildx, :create, "--use", "--name", config.service
+  end
+
   private
     def service_filter
       [ "--filter", "label=service=#{config.service}" ]

lib/tasks/mrsk/app.rake

@@ -9,7 +9,15 @@ namespace :mrsk do
 
     desc "Build locally and push app image to registry"
     task :push do
-      run_locally { execute *app.push } unless ENV["VERSION"]
+      run_locally do 
+        begin
+          execute *app.push
+        rescue SSHKit::Command::Failed => e
+          error "Missing compatible buildx builder, so creating a new one first"
+          execute *app.create_new_builder
+          execute *app.push
+        end
+      end unless ENV["VERSION"]
     end
 
     desc "Pull app image from the registry onto servers"