[extensions] Add extension management install command (#6703)

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

@@ -0,0 +1,62 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { CommandModule } from 'yargs';
+import {
+  installExtension,
+  ExtensionInstallMetadata,
+} from '../../config/extension.js';
+
+interface InstallArgs {
+  source?: string;
+  path?: string;
+}
+
+export async function handleInstall(args: InstallArgs) {
+  try {
+    const installMetadata: ExtensionInstallMetadata = {
+      source: (args.source || args.path) as string,
+      type: args.source ? 'git' : 'local',
+    };
+    const extensionName = await installExtension(installMetadata);
+    console.log(
+      `Extension "${extensionName}" installed successfully and enabled.`,
+    );
+  } catch (error) {
+    console.error((error as Error).message);
+    process.exit(1);
+  }
+}
+
+export const installCommand: CommandModule = {
+  command: 'install [--source | --path ]',
+  describe: 'Installs an extension from a git repository or a local path.',
+  builder: (yargs) =>
+    yargs
+      .option('source', {
+        describe: 'The git URL of the extension to install.',
+        type: 'string',
+      })
+      .option('path', {
+        describe: 'Path to a local extension directory.',
+        type: 'string',
+      })
+      .conflicts('source', 'path')
+      .check((argv) => {
+        if (!argv.source && !argv.path) {
+          throw new Error(
+            'Either a git URL --source or a --path must be provided.',
+          );
+        }
+        return true;
+      }),
+  handler: async (argv) => {
+    await handleInstall({
+      source: argv['source'] as string | undefined,
+      path: argv['path'] as string | undefined,
+    });
+  },
+};