Barebones implementation of local builds

package.json

@@ -104,7 +104,7 @@
     ]
   },
   "dependencies": {
-    "@apphosting/build": "^0.1.6",
+    "@apphosting/build": "^0.1.7",
     "@apphosting/common": "^0.0.8",
     "@electric-sql/pglite": "^0.3.3",
     "@electric-sql/pglite-tools": "^0.2.8",
@@ -167,6 +167,7 @@
     "stream-chain": "^2.2.4",
     "stream-json": "^1.7.3",
     "superstatic": "^10.0.0",
+    "tar": "^7.5.11",
     "tcp-port-used": "^1.0.2",
     "tmp": "^0.2.3",
     "triple-beam": "^1.3.0",

src/apphosting/localbuilds.ts

@@ -2,7 +2,17 @@ import { BuildConfig, Env } from "../gcp/apphosting";
 import { localBuild as localAppHostingBuild } from "@apphosting/build";
 
 /**
- * Triggers a local apphosting build.
+ * Triggers a local build of your App Hosting codebase.
+ *
+ * This function orchestrates the build process using the App Hosting build adapter.
+ * It detects the framework (though currently defaults/assumes 'nextjs' in some contexts),
+ * generates the necessary build artifacts, and returns metadata about the build.
+ * @param projectRoot - The root directory of the project to build.
+ * @param framework - The framework to use for the build (e.g., 'nextjs').
+ * @return A promise that resolves to the build output, including:
+ *          - `outputFiles`: Paths to the generated build artifacts.
+ *          - `annotations`: Metadata annotations relating to the build.
+ *          - `buildConfig`: Configuration derived from the build process (e.g. run commands, environment variables).
  */
 export async function localBuild(
   projectRoot: string,