How to update a forked git repo on github - so it's up-to-date with the original from where it was forked. In other words, how to re-sync your fork with the original - as is needed when updating the Magento 2 code base.
Update your local repo with your remote on github :
git remote -v
origin https://github.com/thelettuce/magento2.git (fetch)
origin https://github.com/thelettuce/magento2.git (push)
git branch
git fetch
git pull
Add an upstream remote of where the fork is from :
git remote add upstream https://github.com/magento/magento2.git
git remote -v
origin https://github.com/thelettuce/magento2.git (fetch)
origin https://github.com/thelettuce/magento2.git (push)
upstream https://github.com/magento/magento2.git (fetch)
upstream https://github.com/magento/magento2.git (push)
Fetch upstream, checkout to your branch and merge it with upstream, then push back to github.
git fetch upstream
git checkout develop
git merge upstream/develop
git push origin
Github is now up to date!