The -m flag can be used with git branch to move/rename an existing
branch. If you are already on the branch that you want to rename, all you
need to do is provide the new branch name.
$ git branch -m <new-branch-name>If you want to rename a branch other than the one you are currently on, you must specify both the existing (old) branch name and the new branch name.
$ git branch -m <old-branch-name> <new-branch-name>h/t Dillon Hafer