strip @id from --provenance output

Author: mr-c

cwltool/main.py

@@ -836,6 +836,18 @@ def my_represent_none(self, data):  # pylint: disable=unused-argument
                 if runtimeContext.research_obj is not None:
                     runtimeContext.research_obj.create_job(
                         out, None, True)
+                    def remove_at_id(doc):  # type: MutableMapping -> None
+                        for key in list(doc.keys()):
+                            if key == '@id':
+                                del doc[key]
+                            else:
+                                value = doc[key]
+                                if isinstance(value, MutableMapping):
+                                    remove_at_id(value)
+                                elif isinstance(value, MutableSequence):
+                                    for entry in value:
+                                        remove_at_id(entry)
+                    remove_at_id(out)
 
                 def loc_to_path(obj):  # type: (Dict[Text, Any]) -> None
                     for field in ("path", "nameext", "nameroot", "dirname"):