fix(zsh): add git_current_branch to git.plugin.zsh

private_dot_config/zsh-plugins/git.plugin.zsh

@@ -16,6 +16,17 @@ function current_branch() {
   git_current_branch
 }
 
+function git_current_branch() {
+  local ref
+  ref=$(__git_prompt_git symbolic-ref --quiet HEAD 2> /dev/null)
+  local ret=$?
+  if [[ $ret != 0 ]]; then
+    [[ $ret == 128 ]] && return  # no git repo.
+    ref=$(__git_prompt_git rev-parse --short HEAD 2> /dev/null) || return
+  fi
+  echo ${ref#refs/heads/}
+}
+
 # Check for develop and similarly named branches
 function git_develop_branch() {
   command git rev-parse --git-dir &>/dev/null || return