cgit

diff --git a/cgitrc.5.txt b/cgitrc.5.txt
index 5903a938c8c4cbe9c5b1e110ae8fbbb787f656f9..8e315786d85917ff16890d411389dad62605bd15 100644
--- a/cgitrc.5.txt
+++ b/cgitrc.5.txt
@@ -42,7 +42,7 @@ 	hh:mm:ss". Default value: "info/web/last-modified".
 
 cache-root::
 	Path used to store the cgit cache entries. Default value:
-	"/var/cache/cgit".
+	"/var/cache/cgit". See also: "MACRO EXPANSION".
 
 cache-dynamic-ttl::
 	Number which specifies the time-to-live, in minutes, for the cached
@@ -161,7 +161,7 @@ 	verbatim at the top of all pages. Default value: none.
 
 include::
 	Name of a configfile to include before the rest of the current config-
-	file is parsed. Default value: none.
+	file is parsed. Default value: none. See also: "MACRO EXPANSION".
 
 index-header::
 	The content of the file specified with this option will be included
@@ -243,7 +243,8 @@
 project-list::
 	A list of subdirectories inside of scan-path, relative to it, that
 	should loaded as git repositories. This must be defined prior to
-	scan-path. Default value: none. See also: scan-path.
+	scan-path. Default value: none. See also: scan-path, "MACRO
+	EXPANSION".
 
 readme::
 	Text which will be used as default value for "repo.readme". Default
@@ -295,7 +296,8 @@ 	directory. If project-list has been defined prior to scan-path,
 	scan-path loads only the directories listed in the file pointed to by
 	project-list. Be advised that only the global settings taken
 	before the scan-path directive will be applied to each repository.
-	Default value: none. See also: cache-scanrc-ttl, project-list.
+	Default value: none. See also: cache-scanrc-ttl, project-list,
+	"MACRO EXPANSION".
 
 section::
 	The name of the current repository section - all repositories defined
@@ -490,6 +492,26 @@ Note that under normal circumstance all these environment variables are
 defined. If however the total size of the defined settings exceed the
 allocated buffer within cgit then only the environment variables that fit
 in the allocated buffer are handed to the filter.
+
+
+MACRO EXPANSION
+---------------
+The following cgitrc options supports a simple macro expansion feature,
+where tokens prefixed with "$" are replaced with the value of a similary
+named environment variable:
+
+- cache-root
+- include
+- project-list
+- scan-path
+
+Macro expansion will also happen on the content of $CGIT_CONFIG, if
+defined.
+
+One usage of this feature is virtual hosting, which in its simplest form
+can be accomplished by adding the following line to /etc/cgitrc:
+
+	include=/etc/cgitrc.d/$HTTP_HOST
 
 
 EXAMPLE CGITRC FILE