# rename your local branch if you are on the branch you want to rename:
$ git branch -m new-name
# rename your local branch if you are on a different branch:
$ git branch -m old-name new-name
# delete the old-name remote branch and push the new-name local branch.
$ git push origin :old-name new-name
# reset the upstream branch for the new-name local branch, switch to the branch and then:
$ git push origin -u new-name