Gem::ConfigFile#write_credentials

# File tmp/rubies/ruby-4.1.0-preview1/lib/rubygems/config_file.rb, line 822
def write_credentials(config)
  dirname = File.dirname credentials_path
  require "fileutils"
  FileUtils.mkdir_p(dirname)

  permissions = 0o600 & ~File.umask
  File.open(credentials_path, "w", permissions) do |f|
    f.write self.class.dump_with_rubygems_yaml(config)
  end
end