fix: download single blob (#16)

While downloading a subtree or a single file, preserve only directories
after the volume path.

dbxio/__init__.py

@@ -4,4 +4,4 @@
 from dbxio.utils import *  # noqa: F403
 from dbxio.volume import *  # noqa: F403
 
-__version__ = '0.4.2'  # single source of truth
+__version__ = '0.4.3'  # single source of truth

dbxio/blobs/download.py

@@ -22,8 +22,7 @@ def download_blob_tree(
         relative_blob_path = blob.name[len(prefix_path) + 1 :] if prefix_path else blob.name
         if not relative_blob_path:
             # if the prefix path is full path to one file
-            assert object_storage_client.blobs_path, 'blobs_path is not set'
-            relative_blob_path = blob.name[len(object_storage_client.blobs_path) + 1 :]
+            relative_blob_path = Path(blob.name).name
 
         if is_dir:
             if not blob.name.startswith(f'{prefix_path}/'):

dbxio/core/cloud/azure/object_storage.py

@@ -64,6 +64,7 @@ def download_blob(self, blob_name: str) -> bytes:
         return blob_client.download_blob().readall()
 
     def download_blob_to_file(self, blob_name: str, file_path: Union[str, Path]) -> None:
+        Path(file_path).parent.mkdir(parents=True, exist_ok=True)
         with open(file_path, 'wb') as f:
             f.write(self.download_blob(blob_name))