The desired style for class templates is as follows. For short template parameter lists, the class head can be on the same line as template:

template <typename T> class foo {
public:
  int x;
};

The more general form, which is always appropriate, is to separate them onto two lines and indent:

template <typename T>
  class foo {
  public:
    int x;

  private:
    int y;  // exposition only
  };

Any access specifiers other than the first one should be preceded by a newline.

Very long member function templates may need to go on three (or more) lines, also suitably indented:

template <typename T>
  constexpr return_type<typename made_up_from<T>::type>
    some_function(T first, T last);

template <typename T>
  constexpr return_type<typename made_up_from<T>::type>
    some_other_function(         // at most one parameter per line in this style
      T first,
      T last = T(),
      typename iterator_traits<T>::value_type init
        = some_default_value,    // "=" goes onto the continuation line
      bool flag);

Long template parameter lists should be aligned:

template <typename OneType,
          typename AnotherType = decay_t<OneType>>
  class foo;

We violate both the indent and the newline style in a number of places, usually systematically across an entire subclause. It would be nice to remedy that eventually.

Before embarking on any changes, we should also cross-check with the "namespace std" issue (I forget which one that is) to make sure that we either do or do not enclose the entire class definition in a namespace.