zsh: show git repo name, branch in right prompt

zsh-git-prompt.sh

# although StackOverflow has this answer http://stackoverflow.com/a/1128583
# but that code is unreadable, thus I have this (also based on a SO anower: http://stackoverflow.com/a/1128721 )

# get the name of the branch we are on
_git_repo_name() { 
    gittopdir=$(git rev-parse --git-dir 2> /dev/null)
    if [[ "foo$gittopdir" == "foo.git" ]]; then
        echo `basename $(pwd)`
    elif [[ "foo$gittopdir" != "foo" ]]; then
        echo `dirname $gittopdir | xargs basename`
    fi
}
_git_branch_name() {    
    git branch 2>/dev/null | awk '/^\*/ { print $2 }'
}    
 _git_is_dirty() { 
   git diff --quiet 2> /dev/null || echo '*'
 }

autoload -U colors
colors
     
setopt prompt_subst

RPROMPT='$(_git_repo_name) $(_git_branch_name) $(_git_is_dirty)'