I have created a custom field on a managed package object. I know I can retrieve the field or the object using the metadata API
<types>
<members>TheManagedPackageCustomObject__c.MyCustomField__c</members>
<name>CustomField</name>
</types>
<!-OR-->
<types>
<members>TheManagedPackageCustomObject__c</members>
<name>CustomObject</name>
</types>
I don't think I will be able to deploy the whole object that's for sure. So I was wondering if it's possible to deploy this custom field I created in a managed package via ant script ?