Moving current_branch() to git plugin

lib/git.zsh

@@ -11,12 +11,3 @@ parse_git_dirty () {
     echo "$ZSH_THEME_GIT_PROMPT_CLEAN"
   fi
 }
-
-#
-# Will return the current branch name
-# Usage example: git pull origin $(current_branch)
-#
-function current_branch() {
-  ref=$(git symbolic-ref HEAD 2> /dev/null) || return
-  echo ${ref#refs/heads/}
-}