[policy] [PP-1] Branching strategy for post-11.0.x 10.x branches

Problem/Motivation

Assuming that we follow the overall plan in 🌱 [policy] Decide how long major Drupal versions should be supported Needs review we will be creating 10.x minor releases alongside 11.x minor releases.

This means the branches will look something like this:

11.x/main
11.0.x 11.1.x 11.2.x 11.3.x 
10.3.x 10.4.x 10.5.x 10.6.x

For 11.x minors, we can branch off 11.x when we're approaching the minor release.

For 10.x, would we go back to the 'old' way of branching 10.4.x from 10.3.x, or do something different?

One possibility, would be a '10.x' branch which could function as a stable target for backport branches, and we'd then branch the 10.x minors off that near release time.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet