[PATCH] help: add config.troubleshooting section at the top

[timeless at mozdev.org]

# HG changeset patch
# User timeless at mozdev.org
# Date 1443120317 14400
#      Thu Sep 24 14:45:17 2015 -0400
# Node ID 982e500ab6e7ffdc99eac1d1043eb21917f8870e
# Parent  db4c192cb9b3744c42b85af45ea6c8015d271bcc
help: add config.troubleshooting section at the top

diff --git a/mercurial/help/config.txt b/mercurial/help/config.txt
--- a/mercurial/help/config.txt
+++ b/mercurial/help/config.txt
@@ -1,6 +1,19 @@
 The Mercurial system uses a set of configuration files to control
 aspects of its behavior.
 
+Troubleshooting
+===============
+
+If you're having problems with your configuration,
+:hg:`config --debug` can help you understand what is introducing
+a setting into your environment.
+
+See :hg:`help config.syntax` and :hg:`help config.files`
+for information about how and where to override things.
+
+Format
+======
+
 The configuration files use a simple ini-file format. A configuration
 file consists of sections, led by a ``[section]`` header and followed
 by ``name = value`` entries::