Link /latest/ to /stable/ - refs #388

docs/_templates/base.html

@@ -3,4 +3,35 @@
 {% block site_meta %}
 {{ super() }}
 <script defer data-domain="sqlite-utils.datasette.io" src="https://plausible.io/js/plausible.js"></script>
-{% endblock %}
+{% endblock %}
+
+{% block scripts %}
+{{ super() }}
+<script>
+document.addEventListener("DOMContentLoaded", function() {
+  // Show banner linking to /stable/ if this is a /latest/ page
+  if (!/\/latest\//.test(location.pathname)) {
+    return;
+  }
+  var stableUrl = location.pathname.replace("/latest/", "/stable/");
+  // Check it's not a 404
+  fetch(stableUrl, { method: "HEAD" }).then((response) => {
+    if (response.status === 200) {
+      var warning = document.createElement("div");
+      warning.className = "admonition warning";
+      warning.innerHTML = `
+        <p class="first admonition-title">Note</p>
+        <p class="last">
+          This documentation covers the <strong>development version</strong> of Datasette.
+        </p>
+        <p>
+          See <a href="${stableUrl}">this page</a> for the current stable release.
+        </p>
+      `;
+      var mainArticle = document.querySelector("article[role=main]");
+      mainArticle.insertBefore(warning, mainArticle.firstChild);
+    }
+  });
+});
+</script>
+{% endblock %}