# HG changeset patch
# User Joerg Sonnenberger <joerg@bec.de>
# Date 2021-03-15 23:07:12
# Node ID c5912e35d06dc5d40769bb3b929fe93ba823b8aa
# Parent  6b57144792881bb9cda37d43c59d2b8001177981

README: document requirement for builtin zstd

Differential Revision: https://phab.mercurial-scm.org/D10226

diff --git a/README.rst b/README.rst
--- a/README.rst
+++ b/README.rst
@@ -18,3 +18,13 @@ Running without installing::
 
 See https://mercurial-scm.org/ for detailed installation
 instructions, platform-specific notes, and Mercurial user information.
+
+Notes for packagers
+===================
+
+Mercurial ships a copy of the python-zstandard sources. This is used to
+provide support for zstd compression and decompression functionality. The
+module is not intended to be replaced by the plain python-zstandard nor
+is it intended to use a system zstd library. Patches can result in hard
+to diagnose errors and are explicitly discouraged as unsupported
+configuration.