make dest dataset optional

cdsobs/cli/_copy_dataset.py

@@ -50,6 +50,8 @@ def copy_dataset(
 
 
 def _copy_dataset_impl(cdsobs_config_yml, dataset, dest_config_yml, dest_dataset):
+    if dest_dataset is None:
+        dest_dataset = dataset
     check_params(dest_config_yml, dataset, dest_dataset)
 
     try:
@@ -191,7 +193,7 @@ def catalogue_copy(
     for entry in entries:
         # This is needed to load the constraints as it is a deferred attribute.
         # However if we load them the other attributes will dissappear from __dict__
-        # There is no way apparently if doing this better in sqlalchemy
+        # There is no way apparently of doing this better in sqlalchemy
         entry_dict = {
             col.name: getattr(entry, col.name) for col in entry.__table__.columns
         }