Add seed file for container images

db/fixtures/development/26_container_images.rb

+# frozen_string_literal: true
+
+class Gitlab::Seeder::ContainerImages
+  attr_reader :tmp_dir, :project, :images_count
+
+  DOCKER_FILE_CONTENTS = <<~EOS
+    FROM scratch
+    ARG tag
+    ENV tag=$tag
+  EOS
+
+  def initialize(project, images_count)
+    @project = project
+    @images_count = images_count
+    initialize_tmp_dir
+  end
+
+  def seed!
+    images_count.times do |i|
+      image_path = "#{project.container_registry_url}:tag_#{i}"
+      build_image(image_path)
+      push_image(image_path)
+      puts '.'
+    end
+  ensure
+    FileUtils.remove_entry tmp_dir
+  end
+
+  private
+
+  def build_image(image_path)
+    system(*%W[docker build -t #{image_path} --build-arg tag=gitlab_container_image_seed .], chdir: @tmp_dir)
+  end
+
+  def push_image(image_path)
+    system(*%W[docker push #{image_path}], chdir: @tmp_dir)
+  end
+
+  def initialize_tmp_dir
+    @tmp_dir = Dir.mktmpdir('gitlab_seeder_container_images')
+
+    File.write(File.join(@tmp_dir, 'Dockerfile'), DOCKER_FILE_CONTENTS)
+  end
+end
+
+Gitlab::Seeder.quiet do
+  flag = 'SEED_CONTAINER_IMAGES'
+
+  if ENV[flag]
+    admin_user = User.admins.first
+    images_count = Integer(ENV[flag])
+
+    Project.not_mass_generated.visible_to_user(admin_user).sample(1).each do |project|
+      puts "\nSeeding #{images_count} container images to the '#{project.full_path}' project."
+
+      seeder = Gitlab::Seeder::ContainerImages.new(project, images_count)
+      seeder.seed!
+    rescue => e
+      puts "\nSeeding container images failed with #{e.message}."
+      puts "Make sure that the registry is running (https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/howto/registry.md) and that Docker CLI (https://www.docker.com/products/docker-desktop) is installed."
+    end
+  else
+    puts "Skipped. Use the `#{flag}` environment variable to seed container images to the registry."
+  end
+end