site: Redirect / to /docs on production deployments

next.config.js

@@ -1,19 +1,34 @@
 const {withContentlayer} = require('next-contentlayer2');
 /** @type {import('next').NextConfig} */
 
+// in prod, we serve the docs from sourcegraph.com/docs, and this requires special config on the GFE side
+// in preview/development, this is not necessary.
+//
+// VERCEL_ENV is a system env var set by Vercel
+// https://vercel.com/docs/projects/environment-variables/system-environment-variables
+const basePath = process.env.VERCEL_ENV === 'production' ? '/docs' : '';
+
 const nextConfig = {
 	reactStrictMode: true,
 	swcMinify: true,
-	// in prod, we serve the docs from sourcegraph.com/docs, and this requires special config on the GFE side
-	// in preview/development, this is not necessary.
-	//
-	// VERCEL_ENV is a system env var set by Vercel
-	// https://vercel.com/docs/projects/environment-variables/system-environment-variables
-	// basePath: process.env.VERCEL_ENV === 'production' ? '/docs' : '',
-	basePath: process.env.VERCEL_ENV === 'production' ? '/docs' : '',
+	basePath,
 	env: {
-		NEXT_PUBLIC_DOCS_BASE_PATH:
-			process.env.VERCEL_ENV === 'production' ? '/docs' : ''
+		NEXT_PUBLIC_DOCS_BASE_PATH: basePath
+	},
+	// With basePath set, nothing serves `/`, so the *.vercel.app deployment URL
+	// that Vercel links from Slack / GitHub 404s. sourcegraph.com never proxies
+	// `/` to us, so this only affects visitors opening that raw URL. Stay on the
+	// same host so they see this exact deployment, not whatever is live.
+	async redirects() {
+		if (!basePath) return [];
+		return [
+			{
+				source: '/',
+				destination: basePath,
+				basePath: false,
+				permanent: false
+			}
+		];
 	}
 };