Make add-injection support more complex injections. Thanks @PuercoPop.

In short, an injection is now a FUNCTION that takes a
document and returns either a STRING to insert in the
page (possibly with data from the document) or NIL.

NEWS.md

   instead of the previous symlinked, timestamped deploy strategy.
   To retain the previous behavior, add `(versioned)` to your config's
   `:plugins` list.
-* **SITE-BREAKING CHANGE**: Custom themes will be broken by a change
+* **Incompatible Change**: Custom themes will be broken by a change
   to URL handling. Previously, we were hand-constructing URLs in the
   templates. All site objects now store their URL in an instance slot.
   In general, hrefs should be of the form `<a href="{$config.domain}/{$obj.url}"> ...</a>`.
+* **Incompatible Change**: The interface of the `add-injection` function
+  has changed. If you have written a plugin which uses `add-injection`
+  you should update it to conform to the [new interface][add-inj-new].
+* **Docs**: Improved README and Theming docs. New Config File docs.
 * Changes to `:routing` would previously break links in the templates
   but now work seamlessly due to the updated URL handling.
-* **Docs**: Improved README and Theming docs. New Config File docs.
 * Loading content is more robust when empty lines or metadata are passed.
   Thanks to @PuercoPop for the bug report and preliminary fix.
 * The config `:repo` option is now deprecated as its value has become
 * The templates are now HTML5 valid thanks to @Ferada.
 * Fixed a bug where RSS/Atom tag feeds were being published multiple times.
 
+[add-inj-new]: https://github.com/redline6561/coleslaw/blob/master/docs/plugin-api.md#extension-points
+
 ## Changes for 0.9.5 (2014-06-13):
 
 * A plugin for Incremental builds, cutting runtime for generating

docs/hacking.md

 Currently, there is only 1 content type: POST, for blog entries.
 PAGE, a content type for static page support, is available as a plugin.
 
-## Areas for Improvement
+## Areas for Improvement (i.e. The Roadmap)
 
 ### TODO for 0.9.6
 

docs/plugin-api.md

 
 # Extension Points
 
-* **New functionality via JS**, for example the Disqus and Mathjax
-  plugins. In this case, the plugin's `enable` function should call
+* **New functionality via JS**, for example the Disqus and Mathjax plugins.
+  In this case, the plugin's `enable` function should call
   [`add-injection`](http://redlinernotes.com/docs/coleslaw.html#add-injection_func)
-  with an injection and a keyword. The injection itself is a list of
-  the string to insert and a lambda or function that can be called on
-  a content instance to determine whether the injection should be
-  included on the page. The keyword specifies whether the injected
-  text goes in the HEAD or BODY element. The
+  with an injection and a keyword. The injection is a function that takes a
+  *Document* and returns a string to insert in the page or nil.
+  The keyword specifies whether the injected text goes in the HEAD or BODY element. The
   [Disqus plugin](http://github.com/redline6561/coleslaw/blob/master/plugins/disqus.lisp)
   is a good example of this.
 

plugins/analytics.lisp

 </script>")
 
 (defun enable (&key tracking-code)
-  (add-injection (format nil *analytics-js* tracking-code) :head))
+  (let ((snippet (format nil *analytics-js* tracking-code)))
+    (add-injection (constantly snippet) :head)))

plugins/disqus.lisp

      <a href=\"http://disqus.com\" class=\"dsq-brlink\">comments powered by <span class=\"logo-disqus\">Disqus</span></a>")
 
 (defun enable (&key shortname)
-  (add-injection (list (format nil *disqus-header* shortname)
-                       (lambda (x) (typep x 'post))) :body))
+  (flet ((inject-p (x)
+           (when (typep x 'post)
+             (format nil *disqus-header* shortname))))
+    (add-injection #'inject-p :body)))

plugins/mathjax.lisp

 
 (defun enable (&key force config (preset "TeX-AMS-MML_HTMLorMML")
                  (location "http://cdn.mathjax.org/mathjax/latest/MathJax.js"))
-  (flet ((plugin-p (x) (or force (mathjax-p x))))
-    (let ((mathjax-header (format nil *mathjax-header* config location preset)))
-      (add-injection (list mathjax-header #'plugin-p) :head))))
+  (flet ((inject-p (x)
+           (when (or force (mathjax-p x))
+             (format nil *mathjax-header* config location preset))))
+    (add-injection #'inject-p :head)))

src/themes.lisp

   "A list that stores pairs of (string . predicate) to inject in the page.")
 
 (defun add-injection (injection location)
-  "Adds an INJECTION to a given LOCATION for rendering. The INJECTION should be
-a string which will always be added or a (string . lambda). In the latter case,
-the lambda takes a single argument, a content object, i.e. a POST or INDEX, and
-any return value other than nil indicates the injection should be added."
-  (let ((result (etypecase injection
-                  (string (list injection #'identity))
-                  (list injection))))
-    (push result (getf *injections* location))))
+  "Adds an INJECTION to a given LOCATION for rendering. The INJECTION should be a
+function that takes a DOCUMENT and returns NIL or a STRING for template insertion."
+  (push result (getf *injections* location)))
 
 (defun find-injections (content)
   "Iterate over *INJECTIONS* collecting any that should be added to CONTENT."
   (flet ((injections-for (location)
-           (loop for (injection predicate) in (getf *injections* location)
-              when (funcall predicate content)
-              collect injection)))
+           (loop for injection in (getf *injections* location)
+              collecting (funcall injection content))))
     (list :head (injections-for :head)
           :body (injections-for :body))))