zimfw/modules/git/functions/git_current_branch

# slightly modified git_current_branch from oh-my-zsh for theme compatibility
local ref
ref=$(command git symbolic-ref --quiet HEAD 2> /dev/null)
local ret=${?}
if [[ ${ret} != 0 ]]; then
  [[ ${ret} == 128 ]] && return  # no git repo.
  ref=$(command git rev-parse --short HEAD 2> /dev/null) || return
fi
print ${ref#refs/heads/}