--- a/mercurial/help/config.txt	Sat Oct 18 21:48:38 2014 +0200
+++ b/mercurial/help/config.txt	Thu Sep 04 21:36:35 2014 +0200
@@ -38,6 +38,7 @@
   - ``<install-root>/etc/mercurial/hgrc.d/*.rc`` (per-installation)
   - ``/etc/mercurial/hgrc`` (per-system)
   - ``/etc/mercurial/hgrc.d/*.rc`` (per-system)
+  - ``<internal>/default.d/*.rc`` (defaults)
 
 .. container:: verbose.windows
 
@@ -51,6 +52,7 @@
   - ``<install-dir>\Mercurial.ini`` (per-installation)
   - ``<install-dir>\hgrc.d\*.rc`` (per-installation)
   - ``HKEY_LOCAL_MACHINE\SOFTWARE\Mercurial`` (per-installation)
+  - ``<internal>/default.d/*.rc`` (defaults)
 
   .. note::
 
@@ -67,6 +69,7 @@
   - ``<install-root>/lib/mercurial/hgrc.d/*.rc`` (per-installation)
   - ``/lib/mercurial/hgrc`` (per-system)
   - ``/lib/mercurial/hgrc.d/*.rc`` (per-system)
+  - ``<internal>/default.d/*.rc`` (defaults)
 
 Per-repository configuration options only apply in a
 particular repository. This file is not version-controlled, and
@@ -102,6 +105,13 @@
 executed by any user in any directory. Options in these files
 override per-installation options.
 
+Mercurial comes with some default configuration. The default configuration
+files are installed with Mercurial and will be overwritten on upgrades. Default
+configuration files should never be edited by users or administrators but can
+be overridden in other configuration files. So far the directory only contains
+merge tool configuration but packagers can also put other default configuration
+there.
+
 Syntax
 ======