[Docs] Add subfolder docs (#500)

* [Docs] Add subfolder docs

* Apply suggestions from code review
Co-authored-by: Pedro Cuenca <pedro@huggingface.co>

* up
Co-authored-by: Pedro Cuenca <pedro@huggingface.co>

src/diffusers/configuration_utils.py

@@ -134,10 +134,9 @@ class ConfigMixin:
                 The specific model version to use. It can be a branch name, a tag name, or a commit id, since we use a
                 git-based system for storing models and other artifacts on huggingface.co, so `revision` can be any
                 identifier allowed by git.
-            mirror (`str`, *optional*):
-                Mirror source to accelerate downloads in China. If you are from China and have an accessibility
-                problem, you can set this option to resolve it. Note that we do not guarantee the timeliness or safety.
-                Please refer to the mirror site for more information.
+            subfolder (`str`, *optional*, defaults to `""`):
+                In case the relevant files are located inside a subfolder of the model repo (either remote in
+                huggingface.co or downloaded locally), you can specify the folder name here.
 
         <Tip>
 
@@ -175,6 +174,7 @@ class ConfigMixin:
         use_auth_token = kwargs.pop("use_auth_token", None)
         local_files_only = kwargs.pop("local_files_only", False)
         revision = kwargs.pop("revision", None)
+        _ = kwargs.pop("mirror", None)
         subfolder = kwargs.pop("subfolder", None)
 
         user_agent = {"file_type": "config"}

src/diffusers/modeling_utils.py

@@ -228,6 +228,10 @@ class ModelMixin(torch.nn.Module):
                 The specific model version to use. It can be a branch name, a tag name, or a commit id, since we use a
                 git-based system for storing models and other artifacts on huggingface.co, so `revision` can be any
                 identifier allowed by git.
+            subfolder (`str`, *optional*, defaults to `""`):
+                In case the relevant files are located inside a subfolder of the model repo (either remote in
+                huggingface.co or downloaded locally), you can specify the folder name here.
+
             mirror (`str`, *optional*):
                 Mirror source to accelerate downloads in China. If you are from China and have an accessibility
                 problem, you can set this option to resolve it. Note that we do not guarantee the timeliness or safety.