cf. https://help.github.com/en/articles/syncing-a-fork
git remote -v
origin https://github.com/macghriogair/bitbucket-push-and-pull-request-plugin.git (fetch)
origin https://github.com/macghriogair/bitbucket-push-and-pull-request-plugin.git (push)
upstream https://github.com/jenkinsci/bitbucket-push-and-pull-request-plugin.git (fetch)
upstream https://github.com/jenkinsci/bitbucket-push-and-pull-request-plugin.git (push)
Fetch the branches and their respective commits from the upstream repository. Commits to master will be stored in a local branch, upstream/master.
git fetch upstream
git checkout master
Merge the changes from upstream/master into your local master branch. This brings your fork's master branch into sync with the upstream repository, without losing your local changes.
git merge upstream/master
git push origin master