further improvements to initial load

- Migration process will not crash if duplicate model files are found,
  one in legacy location and the other in new location.
  The model in the legacy location will be deleted in this case.

- Added a hint to stable-diffusion-2.1 telling people it will work best
  with 768 pixel images.

- Added the anything-4.0 model.

ldm/invoke/model_manager.py

@@ -753,16 +753,20 @@ class ModelManager(object):
 
         print('** Legacy version <= 2.2.5 model directory layout detected. Reorganizing.')
         print('** This is a quick one-time operation.')
-        from shutil import move
+        from shutil import move, rmtree
         
         # transformer files get moved into the hub directory
         hub = models_dir / 'hub'
         os.makedirs(hub, exist_ok=True)
         for model in legacy_locations:
-            source = models_dir /model
+            source = models_dir / model
+            dest = hub / model.stem
+            print(f'** {source} => {dest}')
             if source.exists():
-                print(f'DEBUG: Moving {models_dir / model} into hub')
-                move(models_dir / model, hub)
+                if dest.exists():
+                    rmtree(source)
+                else:
+                    move(source, dest)
 
         # anything else gets moved into the diffusers directory
         diffusers = models_dir / 'diffusers'
@@ -773,7 +777,12 @@ class ModelManager(object):
                 if full_path.is_relative_to(hub) or full_path.is_relative_to(diffusers):
                     continue
                 if Path(dir).match('models--*--*'):
-                    move(full_path,diffusers)
+                    dest = diffusers / dir
+                    print(f'** {full_path} => {dest}')
+                    if dest.exists():
+                        rmtree(full_path)
+                    else:
+                        move(full_path,dest)
 
         # now clean up by removing any empty directories
         empty = [root for root, dirs, files, in os.walk(models_dir) if not len(dirs) and not len(files)]