docker auth: improve missing user/pwd

Specify the "missing username and password" error message. This makes debugging the action easier when for example mistyping the username or the password.

Signed-off-by: Frank Villaro-Dixon <frank@vi-di.fr>

src/docker.ts

@@ -24,6 +24,13 @@ export async function loginStandard(registry: string, username: string, password
   if (!username || !password) {
     throw new Error('Username and password required');
   }
+  if (!username) {
+    throw new Error('Username required');
+  }
+  if (!password) {
+    throw new Error('Password required');
+  }
+
 
   const loginArgs: Array<string> = ['login', '--password-stdin'];
   loginArgs.push('--username', username);