Gem::Commands::SetupCommand#remove_old_bin_files

# File tmp/rubies/ruby-4.0.0/lib/rubygems/commands/setup_command.rb, line 468
  def remove_old_bin_files(bin_dir)
    old_bin_files = {
      "gem_mirror" => "gem mirror",
      "gem_server" => "gem server",
      "gemlock" => "gem lock",
      "gemri" => "ri",
      "gemwhich" => "gem which",
      "index_gem_repository.rb" => "gem generate_index",
    }

    old_bin_files.each do |old_bin_file, new_name|
      old_bin_path = File.join bin_dir, old_bin_file
      next unless File.exist? old_bin_path

      deprecation_message = "`#{old_bin_file}` has been deprecated. Use `#{new_name}` instead."

      File.open old_bin_path, "w" do |fp|
        fp.write <<-EOF
#!#{Gem.ruby}

abort "#{deprecation_message}"
    EOF
      end

      next unless Gem.win_platform?

      File.open "#{old_bin_path}.bat", "w" do |fp|
        fp.puts %(@ECHO.#{deprecation_message})
      end
    end
  end