First draft of documentation for the :here directive.

    ;; add a directory hierarchy, recursing but excluding specified patterns

    (:tree DIRECTORY-PATHNAME-DESIGNATOR) |

    ;; add a directory relative to the location of the configuration

    ;; file being read.

    (:here RELATIVE-COMPONENT-DESIGNATOR?) |

    ;; override the defaults for exclusion patterns

    (:exclude PATTERN ...) |

    ;; augment the defaults for exclusion patterns

@section Configuration Directories

Configuration directories consist in files each contains

Configuration directories consist in files each containing

a list of directives without any enclosing @code{(:source-registry ...)} form.

The files will be sorted by namestring as if by @code{string<} and

the lists of directives of these files with be concatenated in order.

(:tree "/home/fare/cl/")

@end example

@subsection The :here directive

The @code{:here} directive is intended to simplify the delivery of

complex libraries, 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

   (:here "src/lisp/")

   (:here "extlib/lisp"))

@end example

@section Shell-friendly syntax for configuration