List the current configured remote repository for your fork.
$ git remote -v
Specify a new remote upstream repository that will be synced with the fork.
$ git remote add upstream https://github.com/UMONS-GFA/ardas.git
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
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