Why does creating new branches in Xcode9 always fail with "not a valid branch name"?

Whenever I try to create a new branch, it says: The name "MY-BRANCH-NAME" is not a valid branch name. I am adding the steps I performed while trying to create a new branch.

Why is this happening?

P.s.- There are no uncommitted changes and everything is pushed to github repository.

Solution

I have the same problem. Looks like an xcode bug.

xcode Version 9.0 beta 3 (9M174d)

I exited xcode, ran up sourcetree and created the new branch, loaded up xcode again and all appears fine. I also replicated the issue with a brand new spritekit game project.

Raised a bug report with apple: https://bugreport.apple.com/web/?problemID=33497210