+@subsection The :here directive
+
+The @code{:here} directive is an absolute pathname designator that
+refers to the directory containing the configuration file currently
+being processed.
+
+The @code{:here} directive is intended to simplify the delivery of
+complex CL systems, and for easy configuration of projects shared through
+revision control systems, in accordance with our design principle that
+each participant should be able to provide all and only the information
+available to him or her.
+
+Consider a person X who has set up the source code repository for a
+complex project with a master directory @file{dir/}. Ordinarily, one
+might simply have the user add a directive that would look something
+like this:
+@example
+ (:tree "path/to/dir")
+@end example
+But what if X knows that there are very large subtrees
+under dir that are filled with, e.g., Java source code, image files for
+icons, etc.? All of the asdf system definitions are contained in the
+subdirectories @file{dir/src/lisp/} and @file{dir/extlib/lisp/}, and
+these are the only directories that should be searched.
+
+In this case, X can put into @file{dir/} a file @file{asdf.conf} that
+contains the following:
+@example
+(:source-registry
+ (:tree (:here "src/lisp/"))
+ (:tree (:here "extlib/lisp"))
+ (:directory (:here "outlier/")))
+@end example
+
+Then when someone else (call her Y) checks out a copy of this
+repository, she need only add
+@example
+(:include "/path/to/my/checkout/directory/asdf.conf")
+@end example
+to one of her previously-existing asdf source location configuration
+files, or invoke @code{initialize-source-registry} with a configuration
+form containing that s-expression. ASDF will find the .conf file that X
+has provided, and then set up source locations within the working
+directory according to X's (relative) instructions.