[Releasing] rethinking the branching scheme / sha1 proposal

[Frederik Gladhorn]

This is independent of Ossi's proposal and tries to solve a different problem.

One of the pain points in this release was the "which sha1 makes it in".
I'd like to propose defining this part as it hopefully solves quite some of 
the issues we had.

So far the procedure is roughly: "whenever whichever merge passes CI around 
the cut-off time is in".

I would like to propose instead that we define a certain time, let's say a 
week, where maintainers pick which sha1 in this time frame should be the one 
used for branching.

This means we get a defined sha1 that goes from
 dev->stable and stable->release
and no longer chase a moving target (some tip of the branch).
To not overly complicate things for most modules where little changes happen 
the release team makes a decision.
In case of a change in the branching system this is still valid in that it 
would define the branching point.

Greetings,
Frederik