Docs: Release strategy for patch/minor versions during development of next major release

[Niznikr]

The problem Situations can arise where a bugfix or new feature needs to be released during work towards a new major release. We should have a defined process for doing so.

The solution A strategy is agreed upon and verified. It will likely involve cherry-picking commits and having a dedicated branch for the other releases (to avoid issues with Changesets). Documentation and/or diagrams are made to inform maintainers.

Additional information A strategy/discussion may be needed for release families in general. At the very least we should address this circumstance.

[daneah]

Some inspiration from Django

[daneah]

As an anecdote, we took the approach of keeping a long-running release/14.0.0 branch going to allow develop to continue getting non-breaking features, and merging breaking features into the release branch. This worked okay, but with a few impacts:

• We would forget to merge develop into the release branch regularly, creating hairy merge conflicts
  • The release branch is in general divergent from develop, so we get more merge conflicts no matter what we do
• Atlassian Changesets seems to read commit authors rather than looking at PR authors, and because we squash commits it looked like @brentswisher had done all the work when it came time to release after merging release/14.0.0 into develop.