api.v0alpha.ReshapeAction.SetFieldFromField(SetFieldFromField)

will set "field" from other field

{
    "name": "string",
    "other_field": {
        "datetime": {
            "years": 0,
            "weeks": 0,
            "days": 0,
            "hours": 0,
            "minutes": 0,
            "seconds": 0,
            "duration": "string"
        }
    }
}