fatal: Cannot update paths and switch to branch 'master' at the same time.

fatal: Cannot update paths and switch to branch ‘master’ at the same time.
Did you intend to checkout ‘origin/master’ which can not be resolved as commit?

‘origin/master’ which can not be resolved as commit
Strange: you need to check your remotes:

git remote -v

And make sure origin is fetched:

git fetch origin

Then:

git branch -avv

(to see if you do have fetched an origin/master branch)

执行上面三句代码，然后再执行：
git checkout -b master origin/master