--- a/README	Tue Aug 28 11:24:50 2018 +0200
+++ b/README	Mon Sep 03 22:05:12 2018 +0200
@@ -79,6 +79,22 @@
     [extensions]
     evolve.serveronly =
 
+Extension Purpose
+=================
+
+The goal of this extension is to provide an appropriate place for code and
+concept related to changeset evolution to mature. In this extension we allow
+for hackier code, unlocking quick experimentation and faster iterations.
+
+In addition, the evolve extensions support a wider set of Mercurial version,
+allowing us to reach a larger user base for feedback. The Evolve extension is
+not tight to the Mercurial release cycle and can release new feature and bug
+fix at a higher rate if necessary.
+
+Once a concept is ready enough, its implementation is moved into Mercurial
+core. The maturation period helped us to get a clearer picture of what was
+needed. During the upstreaming process, we can use this clearer picture to
+clean up the code and upgrade it to an appropriate quality for Mercurial core.
 
 How to Contribute
 =================
@@ -125,3 +141,7 @@
 In addition, we have compatibility branches to check tests on older version of
 Mercurial. They are the "mercurial-x.y" branches. They are used to apply
 expected test change only, no code change should happen there.
+
+test output change from a changeset in core should adds the following line to their description:
+
+CORE-TEST-OUTPUT-UPDATE: <CORE-NODE-ID>