"Cannot update paths and switch to branch at the same time"

I sometimes use the checkout -b option to create a new branch, check it out at the same time and set up tracking in one command.

In a new environment, I get this error:

$ git checkout -b test --track origin/master
fatal: Cannot update paths and switch to branch 'test' at the same time.
Did you intend to checkout 'origin/master' which can not be resolved as commit?

Why does Git not like it? This used to work with the same repo.

'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)

Finally, use git switch instead of the confusing git checkout, with Git 2.23+ (August 2019).

git switch -c test --track origin/master

If you have a typo in your branchname you'll get this same error.

You can get this error in the context of, e.g. a Travis build that, by default, checks code out with git clone --depth=50 --branch=master. To the best of my knowledge, you can control --depth via .travis.yml but not the --branch. Since that results in only a single branch being tracked by the remote, you need to independently update the remote to track the desired remote's refs.

Before:

$ git branch -a
* master
remotes/origin/HEAD -> origin/master
remotes/origin/master

The fix:

$ git remote set-branches --add origin branch-1
$ git remote set-branches --add origin branch-2
$ git fetch

After:

$ git branch -a
* master
remotes/origin/HEAD -> origin/master
remotes/origin/branch-1
remotes/origin/branch-2
remotes/origin/master