Add *last-revision* and export it and GET-UPDATED-FILES.

src/coleslaw.lisp

 (in-package :coleslaw)
 
+(defvar *last-revision* nil
+  "The git revision prior to the last push. For use with GET-UPDATED-FILES.")
+
 (defun main (&optional (repo-dir "") oldrev)
   "Load the user's config file, then compile and deploy the site. Optionally,
 REPO-DIR is the location of the blog repo and OLDREV is the revision prior to
 the last push."
+  (setf *last-revision* oldrev)
   (load-config repo-dir)
   (load-content)
   (compile-theme (theme *config*))

src/packages.lisp

   (:use :cl)
   (:import-from :alexandria #:hash-table-values
                             #:make-keyword
-                            #:mappend
-                            #:compose)
+                            #:mappend)
   (:import-from :cl-fad #:file-exists-p)
   (:import-from :closure-template #:compile-template)
   (:import-from :local-time #:format-rfc1123-timestring)
   (:export #:main
            #:preview
            #:*config*
+           #:*last-revision*
            #:content
            #:post
            #:index
            #:render-text
            #:add-injection
            #:theme-fn
+           #:get-updated-files
            ;; The Document Protocol
            #:add-document
            #:find-all