Ref: https://www.peterdavehello.org/2014/02/update_forked_repository/
Ref: https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/syncing-a-fork
git remote add upstream https://github.com/otheruser/repo.git
git remote -v
git checkout master
git fetch upstream master
git rebase upstream/master
git push origin master
Ref: https://docs.github.com/en/enterprise/2.15/user/articles/checking-out-pull-requests-locally
git ls-remote
git fetch origin pull/<PR#>/head:pr-<PR#>
eg. PR#2 => git fetch origin pull/2/head:pr-2
git checkout pr-<PR#>
eg. PR#2 => git checkout pr-2
git pull origin pull/<PR#>/head
eg. PR#2 => git pull origin pull/2/head