Let us assume you have forked a repository (from https://github.com/project/repository_name). You now have a local version at a given time of the repository repository_name.
git pull https://github.com/project/repository_name cd repository_name
Time flyes and you come back to the local repository and you are not synchronised anymore. So, you need to fetch the new commits from the upstream repo, pull and push into your repository. this is done as follows:
git remote add upstream https://github.com/project/repository_name.git git fetch upstream git pull git merge upstream/master git push