> $ git branch --merged | xargs git branch -d

  does this actually work? `git branch --merged` for me also 
  returns '* master', which when xarg'd would include the '*'
  and also 'master'. I don't want to delete master, and I
  certainly dont want to delete * if it globs.

EDIT: made this into a code block as I have no idea how to make asterisks display.