add join_local

[max-yue]

No description provided.

[kennymckormick]

Hi, @max-yue,
Thanks for the contribution. Meanwhile, I think the change needs to be further justified.

In the current design
By default: model_path is set to the huggingface repo_id. The checkpoint will be automatically downloaded to .cache/huggingface/hub.
If you want to use manually downloaded checkpoints, you just need to set the model_path

In your revised version
If LOCAL_MODEL_ROOT is set, will use osp.join(LOCAL_MODEL_ROOT, repo_id) as the checkpoint path.

For the revised versions, I might have following concerns:

1. repo_id usually follows the format of org_name/model_name. However, after cloning, typically it only keepsmodel_name, so you may need manually move the downloaded ckpt to make your scheme work.
2. If LOCAL_MODEL_ROOT is set, you must use local checkpoints for all VLMs. The automatically downloaded ones will be no longer available.

[max-yue]

it's a feature, you can set LOCAL_MODEL_ROOT to have this feature.
if some users do not want this feature, he or she can always do not set this environment variable.

[kennymckormick]

@max-yue Actually I have found a more elegant way to achieve this. If you are interested, please contact me via email (dhd.efz@gmail.com) or wechat (dhd_efz) and we can have a short discussion.