Delete a local development branch

You cannot delete the branch you are currently on.

Try creating a new branch

git checkout -b new-branch

Then delete the develop branch

git branch -d develop

Adding to Nandu Kalidindi's answer:

When you clone a repo, it will always have a master branch. This master branch, shouldn't be deleted. And if you want to delete it anyway, you must push another branch before, so git will recognize the new pushed branch as the new master branch.

So, in your case, if you want to delete the repo you should try a UNIX command (rm -rf).