Do one time:
wget https://github.com/stas00/git-tools/blob/master/how-to-make-pr/github-make-pr-branch
chmod u+x github-make-pr-branch
sudo cp github-make-pr-branch /usr/bin/

(or put it in your local bin path)
And then any time you want to work on a new huggingface transformers feature, just run:
github-make-pr-branch ssh GITHUB-USERNAME huggingface transformers new-feature

It will:

Fork the project if needed
Set up this fork to track the upstream
Sync your fork to upstream master
Create ‘new-feature’ branch
Set its upstream for an easy push

Now you just need to:
cd transformers-new-feature

do your magic and when ready:
git commit -a
git push

and the PR is ready (just need to go to github and click on PR suggestion to submit)
It, of course, works for any github project.
If this is useful I can make a PR to add instructions to CONTRIBUTING.pm.
This could also be converted in an even simpler script invocation specific to transformers, so it’ll just need:
transformers-pr new-feature

currently it uses an ssh access.
There is also a detailed guide to  How to Make a Pull Request (PR) 2.