Separate code blog from ordinary blog

This can now be done by putting code-only posts in a "clog" folder
instead of the customary "blog". To implement this, the code
checks the path of every file and matches the beginning with the
string "posts/clog/".

Other posts can be moved to a "blog" folder or kept outside as-is;
it doesn't make a difference because everything that is not in
"posts/clog/" is filed into the ordinary blog as a default.

haunt.scm

@@ -118,6 +118,8 @@
        (strong "@badrihippo")
        " or read my "
        ,(animating-a "/blog/" "computer" "blog")
+       " and "
+       ,(animating-a "/clog/" "computer" "code blog")
        ".")
     ))
 
@@ -131,6 +133,16 @@
                 #:big-logo #t)
    sxml->html))
 
+;; We'll need this to compare the beginnings
+;; of strings
+(define (string-head string length)
+  (list->string (list-head (string->list string) length)))
+
+(define (string-starts-with? string match)
+  (let ((match-length (string-length match)))
+    (if (< (string-length string) match-length)
+      #f
+      (equal? (string-head string match-length) match))))
 
 ;; Blog contents
 (define* (post-template post #:key post-link)
@@ -158,6 +170,23 @@
 		     (div ,(or (post-ref post 'summary))))))
 	    posts))))
 
+;; Different slug for code and normal blog
+(define (code-post? post)
+  (string-starts-with? (post-file-name post) "posts/clog/"))
+
+(define (post-slug-category post)
+  (let ((clog-or-blog (if (code-post? post)
+                          "clog/"
+                          "blog/")))
+    (string-append clog-or-blog (post-slug-v2 post))))
+
+(define (posts/blog posts)
+  (filter (lambda (post) (not (code-post? post)))
+          posts))
+
+(define (posts/clog posts)
+  (filter code-post? posts))
+
 (define hippo-haunt-theme
   (theme #:name "Hippo"
 	 #:layout
@@ -173,9 +202,22 @@
       #:default-metadata
       '((author . "Badri Sunderarajan")
         (email  . "badrihippo@disroot.org"))
+      #:posts-directory "posts"
+      #:make-slug post-slug-category
       #:readers (list commonmark-reader)
-      #:builders (list (blog #:prefix "/blog"
-		             #:theme hippo-haunt-theme)
+      #:builders (list (blog #:prefix ""
+		             #:theme hippo-haunt-theme
+                             #:collections
+                             `(("Latest Posts"
+                                "blog/index.html"
+                                ,(lambda (posts)
+                                   (posts/reverse-chronological
+                                    (posts/blog posts))))
+                               ("Code Blog"
+                                "clog/index.html"
+                                ,(lambda (posts)
+                                   (posts/reverse-chronological
+                                    (posts/clog posts))))))
                        index-page
                        (atom-feed)
                        (atom-feeds-by-tag)