Improved git prompt handling

* Improved speed, the first time cd'ing into a git repo the prompt
   returns much faster (for me at least).
 * Prompt is now decorated in nested folders within a git repo. No
   longer check for the '.git' folder.

git.zsh

@@ -11,16 +11,10 @@ ZSH_THEME_GIT_PROMPT_CLEAN=""
 
 # get the name of the branch we are on
 function git_prompt_info() {
-  if [[ -d .git ]]; then
-    ref=$(git symbolic-ref HEAD 2> /dev/null) || return
-    branch=${ref#refs/heads/}
-    CURRENT_BRANCH="$ZSH_THEME_GIT_PROMPT_PREFIX${branch}$(parse_git_dirty)$ZSH_THEME_GIT_PROMPT_SUFFIX"
-  else
-    CURRENT_BRANCH=''
-  fi
-
-  echo $CURRENT_BRANCH
+  ref=$(git-symbolic-ref HEAD 2> /dev/null) || return
+  echo "$ZSH_THEME_GIT_PROMPT_PREFIX${ref#refs/heads/}$(parse_git_dirty)$ZSH_THEME_GIT_PROMPT_SUFFIX"
 }
+
 parse_git_dirty () {
   if [[ $(git status  | tail -n1) != "nothing to commit (working directory clean)" ]]; then
     echo "$ZSH_THEME_GIT_PROMPT_DIRTY"