Allow arbitrary layout of blog repos.

NEWS.md

+## Changes for 0.9.4 (2013-05-05):
+
+* Coleslaw no longer expects a particular repo layout. Use whatever
+  directory hierarchy you like.
+
 ## Changes for 0.9.3 (2013-04-16):
 
 * **INCOMPATIBLE CHANGE**: `page-path` and the `blog` config class are no longer exported.

docs/hacking.md

 
 ## Areas for Improvement
 
-### Allow Arbitrary Repo Structure
-
-Currently, *coleslaw* expects all posts to be in the top-level of the
-blog repo. There is no technical reason that coleslaw should care.
-The only change that needs to be made is to the `do-files` macro
-used during content discovery. In particular, it should probably
-use `cl-fad:walk-directory` instead of `cl-fad:list-directory`.
-
 ### Allow Tagless or Dateless Content
 
 Several users have expected to be able to not supply tags or a date

src/util.lisp

          (loop for ,var in ,klasses do ,@body)))))
 
 (defmacro do-files ((var path &optional extension) &body body)
-  "For each file on PATH, run BODY. If EXTENSION is provided, only run BODY
-on files that match the given extension."
-  (alexandria:with-gensyms (extension-p files)
+  "For each file under PATH, run BODY. If EXTENSION is provided, only run
+BODY on files that match the given extension."
+  (alexandria:with-gensyms (extension-p)
     `(flet ((,extension-p (file)
               (string= (pathname-type file) ,extension)))
-       (let ((,files (cl-fad:list-directory ,path)))
-         (dolist (,var ,(if extension
-                            `(remove-if-not #',extension-p ,files)
-                            files))
-           ,@body)))))
+       (cl-fad:walk-directory ,path (lambda (,var) ,@body)
+                              :follow-symlinks nil
+                              :test (if ,extension
+                                        #',extension-p
+                                        (constantly t))))))
 
 (defmacro with-current-directory (path &body body)
   "Change the current directory to PATH and execute BODY in