Except with explicit permission by a release manager.

Do whatever you want on develop, just don't change master.

We'll re-open master after the beta.

As always, check the calendar at https://www.boost.org/development

6-Mar: Boost 1.70.0 closed for all changes

13-Mar: Boost 1.70.0 beta; master branch re-opened

2-Aug: Release closed for all changes, except by permission of a release manager.

3-Apr: Boost 1.70.0 closed for all changes

10-Apr: Boost 1.70.0 release

-- The release managers