ircd::conf: Update doc related to conf item env vars and the related namespace.

include/ircd/README.md

@@ -2,12 +2,13 @@
 
 #### Project Namespaces
 
-* `IRCD_`     Preprocessor #define, macro, and environmental variables.
+* `IRCD_`     Preprocessor #define and macros.
 * `RB_`       Build system related preprocessor #defines and macros (legacy).
 * `ircd_`     C namespace and demangled bindings.
 * `ircd::`    C++ namespace scope.
 * `X-IRCd-`   HTTP header key namespace.
 * `ircd.`     Matrix event type namespace.
+* `ircd_`     Environmental variables (see: conf.h).
 
 #### What To Include
 

include/ircd/conf.h

@@ -23,6 +23,12 @@
 /// O(1) access to the value contained in their item instance. Administrators
 /// have logarithmic access through this interface using the items map by name.
 ///
+/// All conf::items can be controlled by environmental variables at program
+/// startup. The name of the conf::item in the environment uses underscore
+/// '_' rather than '.' and the environment takes precedence over both defaults
+/// and databased values. This means you can set a conf through an env var
+/// to override a broken value.
+///
 namespace ircd::conf
 {
 	template<class T = void> struct item;  // doesn't exist