Move retro/kickoff doc to PROCESS.md

Signed-off-by: Rémy Coutable <remy@rymai.me>

CONTRIBUTING.md

@@ -540,19 +540,6 @@ There are a few rules to get your merge request accepted:
    See the instructions in that document for help if your MR fails the
    "license-finder" test with a "Dependencies that need approval" error.
 
-## Changes for Stable Releases
-
-Sometimes certain changes have to be added to an existing stable release.
-Two examples are bug fixes and performance improvements. In these cases the
-corresponding merge request should be updated to have the following:
-
-1. A milestone indicating what release the merge request should be merged into.
-1. The label "Pick into Stable"
-
-This makes it easier for release managers to keep track of what still has to be
-merged and where changes have to be merged into.
-Like all merge requests the target should be master so all bugfixes are in master.
-
 ## Definition of done
 
 If you contribute to GitLab please know that changes involve more than just

PROCESS.md

+## GitLab Core Team & GitLab Inc. Team Contributing Process
+
+---
+
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 **Table of Contents**  *generated with [DocToc](https://github.com/thlorenz/doctoc)*
 
-- [GitLab Contributing Process](#gitlab-contributing-process)
+- [GitLab Core Team Contributing Process](#gitlab-core-team-contributing-process)
   - [Purpose of describing the contributing process](#purpose-of-describing-the-contributing-process)
   - [Common actions](#common-actions)
     - [Merge request coaching](#merge-request-coaching)
-  - [Workflow labels](#workflow-labels)
   - [Assigning issues](#assigning-issues)
   - [Be kind](#be-kind)
   - [Feature freeze on the 7th for the release on the 22nd](#feature-freeze-on-the-7th-for-the-release-on-the-22nd)
     - [Between the 1st and the 7th](#between-the-1st-and-the-7th)
     - [On the 7th](#on-the-7th)
     - [After the 7th](#after-the-7th)
+  - [Release retrospective and kickoff](#release-retrospective-and-kickoff)
+    - [Retrospective](#retrospective)
+    - [Kickoff](#kickoff)
   - [Copy & paste responses](#copy-&-paste-responses)
     - [Improperly formatted issue](#improperly-formatted-issue)
     - [Issue report for old version](#issue-report-for-old-version)
@@ -28,7 +34,7 @@
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
-# GitLab Core Team Contributing Process
+---
 
 ## Purpose of describing the contributing process
 
@@ -153,6 +159,29 @@ release should have the correct milestone assigned _and_ have the label
 Merge requests without a milestone and this label will
 not be merged into any stable branches.
 
+## Release retrospective and kickoff
+
+### Retrospective
+
+After each release, we have a retrospective call where we discuss what went well,
+what went wrong, and what we can improve for the next release. The
+[retrospective notes] are public and you are invited to comment on them.
+If you're interested, you can even join the
+[retrospective call][retro-kickoff-call], on the first working day after the
+22nd at 6pm CET / 9am PST.
+
+### Kickoff
+
+Before working on the next release, we have a
+kickoff call to explain what we expect to ship in the next release. The
+[kickoff notes] are public and you are invited to comment on them.
+If you're interested, you can even join the [kickoff call][retro-kickoff-call],
+on the first working day after the 7th at 6pm CET / 9am PST..
+
+[retrospective notes]: https://docs.google.com/document/d/1nEkM_7Dj4bT21GJy0Ut3By76FZqCfLBmFQNVThmW2TY/edit?usp=sharing
+[kickoff notes]: https://docs.google.com/document/d/1ElPkZ90A8ey_iOkTvUs_ByMlwKK6NAB2VOK5835wYK0/edit?usp=sharing
+[retro-kickoff-call]: https://gitlab.zoom.us/j/918821206
+
 ## Copy & paste responses
 
 ### Improperly formatted issue