Situation:
Repo on Github that I want to contribute to: https://github.com/whoever/whatever.git
My fork of that repo on github: git@github.com:myself/whatever.git
Over time the upstream repo is updated but my fork on github does not automatically get those updates. To push the latest changes from https://github.com/whoever/whatever.git to <git@github.com>:myself/whatever.git follows these steps.
Clone our repository:
git clone git@github.com:myself/whatever.git
cd whatever
Add the upstream repo as a remote, and call it upstream:
git remote add upstream https://github.com/whoever/whatever.git
Get all the branches of the upstream repo into remote-tracking branches. These branches will be named upstream/master, upstream/some-feature, etc.
git fetch upstream
Now replay all of the upstream’s commits from the master branch against ours:
git checkout master
git rebase upstream/master
git push