No upstream branch
What's the issue exactly ?

Given an `upstream` remote repository with url `https://github.com/huggingface/datasets.git`, you can totally rebase from `upstream/master`.

It's mentioned at the beginning how to add the `upstream` remote repository

https://github.com/huggingface/datasets/blob/987df6b4e9e20fc0c92bc9df48137d170756fd7b/ADD_NEW_DATASET.md#L10-L14
Feels like the documentation on adding a new dataset is outdated?

https://github.com/huggingface/datasets/blob/987df6b4e9e20fc0c92bc9df48137d170756fd7b/ADD_NEW_DATASET.md#L49-L54

There is no upstream branch on remote. 
No upstream branch 
 Feels like the documentation on adding a new dataset is outdated?

https://github.com/huggingface/datasets/blob/987df6b4e9e20fc0c92bc9df48137d170756fd7b/ADD_NEW_DATASET.md#L49-L54

There is no upstream branch on remote.  
 What's the issue exactly ?

Given an `upstream` remote repository with url `https://github.com/huggingface/datasets.git`, you can totally rebase from `upstream/master`.

It's mentioned at the beginning how to add the `upstream` remote repository

https://github.com/huggingface/datasets/blob/987df6b4e9e20fc0c92bc9df48137d170756fd7b/ADD_NEW_DATASET.md#L10-L14