Differences between git pull origin master & git pull origin/master
git pull origin master和git pull origin/master什么区别？
git pull origin master will pull changes from the origin remote, master branch and merge them to the local checked-out branch.
git pull origin/master will pull changes from the locally stored branch origin/master and merge that to the local checked-out branch. The origin/master branch is essentially a "cached copy" of what was last pulled from origin , which is why it's called a remote branch in git parlance. This might be somewhat confusing.
You can see what branches are available with git branch and git branch -r to see the "remote branches".