I think that a git pull command is an alias for a git fetch and a git merge.
I would like to do a git pull origin master in several steps. It think it could be something like this:
git fetch origin master
git merge <remote fetched branch>
It would be just simply
git fetch origin master
git merge origin/master
The first command fetches master from origin. The second merges the remote into your topic branch.
A git fetch update the remote-tracking branches under refs/remotes/<remote>/.
So the commands should be:
git fetch origin master
git merge refs/remotes/origin/master
Thanks to this answer about the difference between git pull a git fetch.