If you have named a branch incorrectly AND pushed this to the remote repository follow these steps before any other developers get a chance to jump on you and give you shit for not correctly following naming conventions.
1. Rename your local branch.
If you are on the branch you want to rename:
git branch -m new-name
If you are on a different branch:
git branch -m old-name new-name
2. Delete the old-name remote branch and push the new-name local branch.
git push origin :old-name new-name
3. Reset the upstream branch for the new-name local branch.
Switch to the branch and then:
git push origin -u new-name
Or you as a fast way to do that, you can use these 3 steps: command in your terminal
git branch -m old_branch new_branch # Rename branch locally
git push origin :old_branch # Delete the old branch
git push --set-upstream origin new_branch # Push the new branch, set local branch to track the new remote