Supprimer une branche remote
"""
$ git push origin :mabranche
"""

Supprimer une branche locale
"""
$ git branch -d mabranche

ou

$ git branch -d mabranche
"""
La différence entre les 2 (man git-branch) :
"""
-d, --delete
Delete a branch. The branch must be fully merged in its upstream branch, or in
HEAD if no upstream was set with --track or --set-upstream.

   -D
       Delete a branch irrespective of its merged status.

"""