don't assign onto __proto__

Author: substack

index.js

@@ -70,6 +70,7 @@ module.exports = function (args, opts) {
         var o = obj;
         keys.slice(0,-1).forEach(function (key) {
             if (o[key] === undefined) o[key] = {};
+            if (o[key] === {}.__proto__) o[key] = {};
             o = o[key];
         });
 

test/proto.js

@@ -4,5 +4,6 @@ var test = require('tape');
 test('proto pollution', function (t) {
     var argv = parse(['--__proto__.x','123']);
     t.equal({}.x, undefined);
+    t.equal(argv.__proto__.x, 123);
     t.end();
 });