[RFC] Release schedule for X server 21.1

[Povilas Kanapickas]

Hello,

According to my recent testing the master branch is in relatively good
shape. There exist known bugs, but we can start planning the release anyway.

I would like to propose release schedule for Xserver 21.1.

 - 2021-08-16 - Driver ABI freeze
 - 2021-08-30 - 21.1 RC 1
 - every 2 weeks after that: a new RC until the final release

Note that there are no open MRs that affect the driver ABI and which
make sense to merge at this time relatively near the RC phase. Thus for
practical purposes the ABI freeze could as well be today.

Differently than previous releases of the X server, the
`server-21.1-branch` release branch will branch off just before the RC 1
release and not after the final release of 21.1. This is because we want
to remove the code of xwayland DDX for the RC releases as xwayland is
released separately. Accordingly, after RC 1 is released the master
branch will be open again for changes targeting the next release.

Regards,
Povilas Kanapickas