feat: add --manifest flag to pack command (#87)

Allow specifying an external manifest file path with `mcpb pack --manifest <path>`.
The manifest resolves relative to CWD, is validated, injected into the bundle,
and errors immediately if the specified file is not found.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/cli/cli.ts

@@ -101,22 +101,33 @@ program
 program
   .command("pack [directory] [output]")
   .description("Pack a directory into an MCPB extension")
-  .action((directory: string = process.cwd(), output?: string) => {
-    void (async () => {
-      try {
-        const success = await packExtension({
-          extensionPath: directory,
-          outputPath: output,
-        });
-        process.exit(success ? 0 : 1);
-      } catch (error) {
-        console.error(
-          `ERROR: ${error instanceof Error ? error.message : "Unknown error"}`,
-        );
-        process.exit(1);
-      }
-    })();
-  });
+  .option(
+    "-m, --manifest <path>",
+    "Path to manifest file (defaults to manifest.json in directory)",
+  )
+  .action(
+    (
+      directory: string = process.cwd(),
+      output: string | undefined,
+      options: { manifest?: string },
+    ) => {
+      void (async () => {
+        try {
+          const success = await packExtension({
+            extensionPath: directory,
+            outputPath: output,
+            manifestPath: options.manifest,
+          });
+          process.exit(success ? 0 : 1);
+        } catch (error) {
+          console.error(
+            `ERROR: ${error instanceof Error ? error.message : "Unknown error"}`,
+          );
+          process.exit(1);
+        }
+      })();
+    },
+  );
 
 // Unpack command
 program

src/cli/pack.ts

@@ -22,6 +22,7 @@ interface PackOptions {
   extensionPath: string;
   outputPath?: string;
   silent?: boolean;
+  manifestPath?: string;
 }
 
 function formatFileSize(bytes: number): string {
@@ -50,6 +51,7 @@ export async function packExtension({
   extensionPath,
   outputPath,
   silent,
+  manifestPath: customManifestPath,
 }: PackOptions): Promise<boolean> {
   const resolvedPath = resolve(extensionPath);
   const logger = getLogger({ silent });
@@ -60,9 +62,18 @@ export async function packExtension({
     return false;
   }
 
-  // Check if manifest exists
-  const manifestPath = join(resolvedPath, "manifest.json");
+  // Resolve manifest path
+  const manifestPath = customManifestPath
+    ? resolve(customManifestPath)
+    : join(resolvedPath, "manifest.json");
+
   if (!existsSync(manifestPath)) {
+    if (customManifestPath) {
+      // When --manifest is explicitly provided, error immediately
+      logger.error(`ERROR: Manifest file not found: ${customManifestPath}`);
+      return false;
+    }
+
     logger.log(`No manifest.json found in ${extensionPath}`);
     const shouldInit = await confirm({
       message: "Would you like to create a manifest.json file?",
@@ -135,6 +146,15 @@ export async function packExtension({
       mcpbIgnorePatterns,
     );
 
+    // When using a custom manifest path, inject the manifest into the bundle
+    if (customManifestPath) {
+      const manifestStat = statSync(manifestPath);
+      files["manifest.json"] = {
+        data: readFileSync(manifestPath),
+        mode: manifestStat.mode,
+      };
+    }
+
     // Print package header
     logger.log(`\n📦  ${manifest.name}@${manifest.version}`);