update model_manager.py

- read files in chunks when calculating sha
  - windows runner is crashing without

ldm/invoke/model_manager.py

@@ -753,7 +753,7 @@ def search_models(self, search_folder):
         return search_folder, found_models
 
     def _choose_diffusers_vae(self, model_name:str, vae:str=None)->Union[dict,str]:
-        
+
         # In the event that the original entry is using a custom ckpt VAE, we try to
         # map that VAE onto a diffuser VAE using a hard-coded dictionary.
         # I would prefer to do this differently: We load the ckpt model into memory, swap the
@@ -954,7 +954,7 @@ def _push_newest_model(self,model_name:str) -> None:
     def _has_cuda(self) -> bool:
         return self.device.type == 'cuda'
 
-    def _diffuser_sha256(self,name_or_path:Union[str, Path])->Union[str,bytes]:
+    def _diffuser_sha256(self,name_or_path:Union[str, Path],chunksize=4096)->Union[str,bytes]:
         path = None
         if isinstance(name_or_path,Path):
            path = name_or_path
@@ -976,7 +976,8 @@ def _diffuser_sha256(self,name_or_path:Union[str, Path])->Union[str,bytes]:
             for name in files:
                 count += 1
                 with open(os.path.join(root,name),'rb') as f:
-                    sha.update(f.read())
+                    while chunk := f.read(chunksize):
+                        sha.update(chunk)
         hash = sha.hexdigest()
         toc = time.time()
         print(f'  | sha256 = {hash} ({count} files hashed in','%4.2fs)' % (toc - tic))