# HG changeset patch
# User Patrick Mezard <pmezard@gmail.com>
# Date 1182368141 -7200
# Node ID 54b735135fd30798f959b7422321ebf1adc7d8ab
# Parent  c7371aa0c153af7e469e03762eb119b9f936996e
Document empty environment variables not being passed to hooks under Windows.

diff --git a/doc/hgrc.5.txt b/doc/hgrc.5.txt
--- a/doc/hgrc.5.txt
+++ b/doc/hgrc.5.txt
@@ -308,6 +308,11 @@ hooks::
   did not have a "HG_" prefix.  The old unprefixed names are no longer
   provided in the environment.
 
+  Note2: Environment variables with empty values may not be passed to
+  hooks on platforms like Windows. For instance, $HG_PARENT2 will
+  not be available under Windows for non-merge changesets while being
+  set to an empty value under Unix-like systems.
+
   The syntax for Python hooks is as follows:
 
     hookname = python:modulename.submodule.callable