Released: June 21, 2022

IMPORTANT: This release deprecates views::group_by which was
an endless source of confusion. group_by is replaced with
views::chunk_by (which, beware, has subtly different semantics,
see below.)

Changes:

• NEW: views::chunk_by which, like the old views::group_by it replaces,
  splits a range into a range-of-ranges, where adjacent elements satisfy a binary
  predicate (#1648). [Note: Whereas views::group_by evaluated the predicate
  between the current element and the first element in the chunk, views::chunk_by
  evaluates the predicate between adjacent elements. -- end note]
• NEW: constexpr all the algorithms that are constexpr in C++20's std::ranges
  (#1683).
• NEW: Fold algorithms from P2322 (#1628), (#1668).
• NEW: ranges::unformatted_ostream_iterator (#1586).
• NEW: Support for the build2 build system (#1562).
• Implement P2328: relax the constraint on ranges::join_view
  to support joining ranges of prvalue non-view ranges (#1655).
• Improved algorithm for ranges::linear_distribute (#1679).
• Renamed safe_subrange_t to borrowed_subrange_t (#1542).
• Extend ranges::to to support conversion to container-of-containers (#1553).
• views::enumerate can be a borrowed_view (#1571).
• ranges::upper_bound works in the presence of overloaded operator& (#1632).
• Input iterators are no longer required to be default-constructible (#1652).

Bugs fixed:

• ranges::to<std::map>(v) does not work (#1700)
• ranges::reverse_iterator has the wrong value_type when reversing a proxy
  range (#1670).
• A post-increment of a ranges::counted_iterator wrapping an input iterator with
  a void-returning post-increment operator isn't incrementing the count (#1664).
• Bad assert in views::drop_last (#1599).
• Read of uninitialized bool in views::cache1 (#1610).
• ranges::unstable_remove_if calls predicate on same element twice (#1629).
• ranges::on(f,g)(x...) should be f(g(x)...) instead of f(g(x...)) (#1661).
• Broken qualification of cmake targets (#1557).
• Various portability and documentation fixes.

Credits: I would like to thank the following people who contributed to this release
(in no particular order): Barry Revzin, @dvirtz, Gonzalo Brito, Johel Ernesto Guerrero
Peña, Joël Lamotte, Doug Roeper, Facundo Tuesca, Vitaly Zaitsev, @23rd, @furkanusta,
Jonathan Haigh, @SmorkalovG, @marehr, Matt Beardsley, Chris Glover, Louis Dionne, Jin
Shang (@js8544), Hui Xie, @huixie90, Robert Maynard, Silver Zachara, @sergegers,
Théo DELRIEU, @LesnyRumcajs, Yehezkel Bernat, Maciej Patro, Klemens Nanni, Thomas
Madlener, and Jason Merrill.

🎉 Special thanks to Barry Revzin for stepping up to be part-time co-maintainer of
range-v3. 🎉