Document the ZConfig.cmdline module.

doc/ZConfig/zconfig.tex

@@ -1140,6 +1140,41 @@ The following methods can be used as utilities:
 \end{methoddesc}
 
 
+\section{\module{ZConfig.cmdline} --- Command-line override support}
+
+\declaremodule{}{ZConfig.cmdline}
+\modulesynopsis{Support for command-line overrides for configuration
+                settings.}
+
+This module exports an extended version of the \class{ConfigLoader}
+class from the \refmodule{ZConfig.loader} module.  This provides
+support for overriding specific settings from the configuration file
+from the command line, without requiring the application to provide
+specific options for everything the configuration file can include.
+
+\begin{classdesc}{ExtendedConfigLoader}{schema}
+  Construct a \class{ConfigLoader} subclass that adds support for
+  command-line overrides.
+\end{classdesc}
+
+The following additional method is provided, and is the only way to
+provide position information to associate with command-line
+parameters:
+
+\begin{methoddesc}{addOption}{spec\optional{, pos}}
+  Add a single value to the list of overridden values.  The \var{spec}
+  argument is a value specified, as described for the
+  \function{\refmodule{ZConfig}.loadConfig()} function.  A source
+  position for the specifier may be given as \var{pos}.  If \var{pos}
+  is specified and not \code{None}, it must be a sequence of three
+  values.  The first is the URL of the source (or some other
+  identifying string).  The second and third are the line number and
+  column of the setting.  These position information is only used to
+  construct a \exception{DataConversionError} when data conversion
+  fails.
+\end{methoddesc}
+
+
 \section{\module{ZConfig.substitution} --- String substitution}
 
 \declaremodule{}{ZConfig.substitution}