brew/Library/Homebrew/utils/svn.rb

module Utils
  def self.clear_svn_version_cache
    remove_instance_variable(:@svn) if instance_variable_defined?(:@svn)
  end

  def self.svn_available?
    return @svn if instance_variable_defined?(:@svn)

    @svn = quiet_system HOMEBREW_SHIMS_PATH/"scm/svn", "--version"
  end

  def self.svn_remote_exists?(url)
    return true unless svn_available?

    ssl_args = ["--non-interactive", "--trust-server-cert"] if ENV["HOMEBREW_TEST_ONLINE"]
    quiet_system "svn", "ls", url, "--depth", "empty", *ssl_args
  end
end