Automatically converts the active SD V1.5 model in to an inpainting model when starting an inpainting gen.

Please note:

• This will download a 1.68 GB model when activated for the first time.
• This only supports checkpoints based on SD 1.5. I'm not planning to add support for other versions of SD.

Inspired by: https://github.com/hako-mikan/sd-webui-supermerger 🙏