Read https://help.github.com/categories/collaborating-with-issues-and-pull-requests/
from https://www.digitalocean.com/community/tutorials/how-to-rebase-and-update-a-pull-request
- git clone https://github.com/martinus/bitcoin.git
- git remote add upstream https://github.com/bitcoin/bitcoin.git
- git fetch upstream
- git remote -v