Fixed dirty check to include files added to index

lib/git.zsh

@@ -13,7 +13,7 @@ parse_git_dirty() {
     if [[ $POST_1_7_2_GIT -gt 0 ]]; then
           SUBMODULE_SYNTAX="--ignore-submodules=dirty"
     fi
-    if [[ -n $(git diff ${SUBMODULE_SYNTAX} 2> /dev/null) ]]; then
+    if [[ -n $(git diff ${SUBMODULE_SYNTAX} HEAD 2> /dev/null) ]]; then
       echo "$ZSH_THEME_GIT_PROMPT_DIRTY"
     else
       echo "$ZSH_THEME_GIT_PROMPT_CLEAN"