git fetch # This updates 'remote' portion of local repo.
git reset --hard origin/<your-working-branch>
# this will sync your local copy with remote content, discarding any committed
# or uncommitted changes.
fatal: 'upstream/master' does not appear to be a git repository
fatal: Could not read from remote repository.
Please make sure you have the correct access rights and the repository exists.
Now run the below command.
git fetch upstream
Now if you are on master then merge the upstream/master into master branch
git merge upstream/master
That's it!!
Crosscheck via git remote command, more specific git remote -v
If I also have commit rights to the upstream repo, I can create a local upstream branch and do work that will go upstream there.