Same thing here.
The trick is to have one repo with two remote so that in my case:
origin/master points to pytorch’s master branch
albanD/my-feature points to a branch in my fork.
If I want to update with pytorch’s master:
git co master
git pull
git co my-feature
git rebase master

And now your branch is up to date with master.
Also don’t worry about have too many commits on the PR: our merging process will take care of cleaning any extra commit !