I forked a repo from github.com, and also had set the upstream remote. Below is my repo
[ Leezhm LIZHM ~/Developments/OF_GIT ] git remote -v
origin git@github.com:leezhm/openFrameworks.git (fetch)
origin git@github.com:leezhm/openFrameworks.git (push)
upstream https://github.com/openframeworks/openFrameworks.git (fetch)
upstream https://github.com/openframeworks/openFrameworks.git (push)
when I used this command
git fetch upstream develop
git merge upstream/mac8
It always got the following error
fatal: 'upstream/mac8' does not point to a commit