Use grep to detect if untracked files exist instead of storing all the output of ls-files.

themes/steeef.zsh-theme

@@ -81,7 +81,7 @@ add-zsh-hook chpwd steeef_chpwd
 function steeef_precmd {
     if [[ -n "$PR_GIT_UPDATE" ]] ; then
         # check for untracked files or updated submodules, since vcs_info doesn't
-        if [[ ! -z $(git ls-files --other --exclude-standard 2> /dev/null) ]]; then
+        if git ls-files --other --exclude-standard 2> /dev/null | grep -q "."; then
             PR_GIT_UPDATE=1
             FMT_BRANCH="(%{$turquoise%}%b%u%c%{$hotpink%}●${PR_RST})"
         else