Dynamically fetch latest stable release installer

Fetch the install-linux-release asset from the latest GitHub release
instead of pointing to the main branch. Falls back to main branch URL
if the API call fails. The endpoint now serves immutable release assets
with a 5-minute CDN cache.

Author: rgbkrk

README.md

@@ -6,10 +6,9 @@ nteract Linux installer.
 The endpoint intentionally stays separate from the marketing site. It serves
 plain shell, not HTML, and it does not install agent-specific integrations.
 
-The bootstrap currently downloads the merged desktop installer from
-`raw.githubusercontent.com/nteract/desktop/main/scripts/install-linux-release`.
-If desktop releases later publish the installer as a release asset, switch the
-bootstrap URL to that immutable release asset.
+The bootstrap dynamically fetches the latest stable release's
+`install-linux-release` asset from GitHub releases. Falls back to the main
+branch version if the API call fails.
 
 ## Local development
 

api/index.js

@@ -1,8 +1,10 @@
-import { installerScript } from "../lib/script.js";
+import { installerScript, getLatestStableInstallerUrl } from "../lib/script.js";
 
-export default function handler(request, response) {
+export default async function handler(request, response) {
   response.setHeader("Content-Type", "text/x-shellscript; charset=utf-8");
   response.setHeader("Cache-Control", "public, max-age=300, s-maxage=300");
   response.setHeader("X-Content-Type-Options", "nosniff");
-  response.status(200).send(installerScript());
+
+  const installerUrl = await getLatestStableInstallerUrl();
+  response.status(200).send(installerScript(installerUrl));
 }

lib/script.js

@@ -1,7 +1,29 @@
-const DEFAULT_INSTALLER_URL =
+const FALLBACK_INSTALLER_URL =
   "https://raw.githubusercontent.com/nteract/desktop/main/scripts/install-linux-release";
 
-export function installerScript(installerUrl = DEFAULT_INSTALLER_URL) {
+/**
+ * Fetch the latest stable release's install-linux-release asset URL.
+ * Returns fallback URL on error.
+ */
+export async function getLatestStableInstallerUrl() {
+  try {
+    const res = await fetch(
+      "https://api.github.com/repos/nteract/desktop/releases/latest",
+      {
+        headers: { Accept: "application/vnd.github.v3+json" },
+      }
+    );
+    if (!res.ok) return FALLBACK_INSTALLER_URL;
+
+    const release = await res.json();
+    const asset = release.assets?.find((a) => a.name === "install-linux-release");
+    return asset?.browser_download_url || FALLBACK_INSTALLER_URL;
+  } catch {
+    return FALLBACK_INSTALLER_URL;
+  }
+}
+
+export function installerScript(installerUrl) {
   return `#!/bin/sh
 set -eu