[extensions] Add extensions update command (#6878)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/cli/src/commands/extensions/update.ts

@@ -0,0 +1,46 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { CommandModule } from 'yargs';
+import { updateExtension } from '../../config/extension.js';
+
+interface UpdateArgs {
+  name: string;
+}
+
+export async function handleUpdate(args: UpdateArgs) {
+  try {
+    // TODO(chrstnb): we should list extensions if the requested extension is not installed.
+    const updatedExtensionInfo = await updateExtension(args.name);
+    if (!updatedExtensionInfo) {
+      console.log(`Extension "${args.name}" failed to update.`);
+      return;
+    }
+    console.log(
+      `Extension "${args.name}" successfully updated: ${updatedExtensionInfo.originalVersion} → ${updatedExtensionInfo.updatedVersion}.`,
+    );
+  } catch (error) {
+    console.error((error as Error).message);
+    process.exit(1);
+  }
+}
+
+export const updateCommand: CommandModule = {
+  command: 'update <name>',
+  describe: 'Updates an extension.',
+  builder: (yargs) =>
+    yargs
+      .positional('name', {
+        describe: 'The name of the extension to update.',
+        type: 'string',
+      })
+      .check((_argv) => true),
+  handler: async (argv) => {
+    await handleUpdate({
+      name: argv['name'] as string,
+    });
+  },
+};