Custom path to a shared .ckpt file?

[ack226]

Is it possible to specify a custom path to the .ckpt model weights file instead of requiring it to be in \stable-diffusion\models\ldm\stable-diffusion-v1\model.ckpt?

This would be useful for:

1. Sharing one model file between multiple installations, for example when a user has both the stable and the dev versions of of this repo running, thus saving disk space vs. requiring copies in multiple directories.
2. Easily switching between different model files without moving the files around. For example, using the "full-ema" model vs. the main model, or moving back and forth between 1.4 and 1.5 once it's available.