Fix incorrectly issued 301 redirects on latest for project roots

This commit adds a small piece of Javascript code to force browsers to forget
about incorrectly issued 301 redirects from "latest" versions.
This code only runs for root project paths (i.e. `/linux/v6.10.2/source`, but
not `/linux/v6.10.2/source/arch`) - other links with "latest" will remain
broken for people who visited them (at least until they clear their cache).

http/script.js

@@ -162,4 +162,23 @@ window.requestAnimationFrame(offsetAnchor)
 // in case of slow rendering very long pages.
 window.onload = function () {
   window.requestAnimationFrame(offsetAnchor)
+
+  // fix incorrectly issued 301 redirect
+  // https://developer.mozilla.org/en-US/docs/Web/API/Request/cache
+  // https://developer.mozilla.org/en-US/docs/Web/API/Request/redirect
+  // TODO: remove after 10.2024
+  let path = location.pathname.split('/');
+  if (path.length == 4) {
+    path[2] = 'latest';
+    let newPath = path.join('/');
+    fetch(newPath, {
+        cache: 'reload',
+        redirect: 'manual',
+        // this is to make sure that varnish will cache the response,
+        // by default fetch sends no-cache in both headers if cache='reload'
+        headers: {'Cache-Control': 'max-age=86400', 'Pragma': ''}
+    })
+      .then(console.log)
+      .catch(console.error);
+  }
 }

templates/layout.html

@@ -44,7 +44,7 @@
                 <span class="poweredby">powered by <a target="_blank" href="https://github.com/bootlin/elixir">Elixir 2.2</a></span>
             </footer>
         </div>
-        <script src="/script.js?v=3"></script>
+        <script src="/script.js?v=4"></script>
         <script src="/dynamic-references.js?v=4"></script>
         <script src="/autocomplete.js" project="{{ current_project }}"></script>
     </body>