sidedata-exchange: rewrite sidedata on-the-fly whenever possible When a A exchanges with B, the difference of their supported sidedata categories is made, and the responsibility is always with the client to generated it: - If A pushes to B and B requires category `foo` that A does not have, A will need to generate it when sending it to B. - If A pulls from B and A needs category `foo`, it will generate `foo` before the end of the transaction. - Any category that is not required is removed. If peers are not compatible, abort. It is forbidden to rewrite sidedata for a rev that already has sidedata, since that would introduce unreachable (garbage) data in the data file, something we're not prepared for yet. Differential Revision: https://phab.mercurial-scm.org/D10032

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/testlib/ext-sidedata-4.py	Fri Feb 19 11:24:50 2021 +0100
@@ -0,0 +1,19 @@
+# coding: utf8
+# ext-sidedata-4.py - small extension to test (differently still) the sidedata
+# logic
+#
+# Simulates a server for a complex sidedata exchange.
+#
+# Copyright 2021 Raphaël Gomès <rgomes@octobus.net>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+from mercurial.revlogutils import sidedata
+
+
+def reposetup(ui, repo):
+    repo.register_wanted_sidedata(sidedata.SD_TEST2)
+    repo.register_wanted_sidedata(sidedata.SD_TEST3)