Fix software environment and use channels+manifest setup

.gitlab-ci.yml

@@ -7,12 +7,10 @@ pages:
   # Export the example page to HTML and publish it alongside with the template
   # sources to the GitLab page.
   - >
-    guix environment --pure --ad-hoc coreutils which wget emacs emacs-org2web
-    emacs-org emacs-org-contrib emacs-htmlize -- emacs --batch --no-init-file
-    --eval '(setq org-confirm-babel-evaluate nil)' --load pages.el --funcall
-    org-publish-all
-  # Set the example page to be the index page of the GitLab page.
-  - mv ./public/example.html ./public/index.html
+    guix time-machine -C channels.scm -- shell --pure coreutils which wget emacs
+    emacs-org2web emacs-org emacs-org-contrib emacs-htmlize -- emacs --batch
+    --no-init-file --eval '(setq org-confirm-babel-evaluate nil)'
+    --load pages.el --funcall org-publish-all
   artifacts:
     paths:
     - public

channels.scm

+(list
+ (channel
+  (name 'guix)
+  (url "https://git.savannah.gnu.org/git/guix.git")
+  (commit "eb34ff16cc9038880e87e1a58a93331fca37ad92")))

manifest.scm

+(specifications->manifest
+  (list "coreutils"
+        "which"
+        "wget"
+        "emacs"
+        "emacs-org2web"
+        "emacs-org"
+        "emacs-org-contrib"
+        "emacs-htmlize"))