relnotes/next

--- a/relnotes/next	Wed Mar 10 18:09:21 2021 +0100
+++ b/relnotes/next	Wed Jan 13 16:14:58 2021 +0100
@@ -43,3 +43,7 @@
    now get a revision number as argument instead of a node.
 
  * revlog.addrevision returns the revision number instead of the node.
+
+ * `nodes.nullid` and related constants are being phased out as part of
+   the deprecation of SHA1. Repository instances and related classes
+   provide access via `nodeconstants` and in some cases `nullid` attributes.