Configuring a remote for a fork

1. Open Terminal.
2. List the current configured remote repository for your fork.

$ git remote -v
> origin  https://github.com/YOUR_USERNAME/YOUR_FORK.git (fetch)
> origin  https://github.com/YOUR_USERNAME/YOUR_FORK.git (push)

3 Specify a new remote upstream repository that will be synced with the fork.

$ git remote add upstream https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git

4. Verify the new upstream repository you've specified for your fork.

$ git remote -v
> origin    https://github.com/YOUR_USERNAME/YOUR_FORK.git (fetch)
> origin    https://github.com/YOUR_USERNAME/YOUR_FORK.git (push)
> upstream  https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git (fetch)
> upstream  https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git (push)

Syncing a fork

1. Change the current working directory to your local project.
2. 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
> remote: Counting objects: 75, done.
> remote: Compressing objects: 100% (53/53), done.
> remote: Total 62 (delta 27), reused 44 (delta 9)
> Unpacking objects: 100% (62/62), done.
> From https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY
>  * [new branch]      master     -> upstream/master

Check out your fork's local master branch.

$ git checkout master
> Switched to branch '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
> Updating a422352..5fdff0f
> Fast-forward
>  README                    |    9 -------
>  README.md                 |    7 ++++++
>  2 files changed, 7 insertions(+), 9 deletions(-)
>  delete mode 100644 README
>  create mode 100644 README.md

https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/syncing-a-fork

https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/configuring-a-remote-for-a-fork