Fix error in bare git repositories

prompt_fred_setup

@@ -25,10 +25,15 @@ prompt_context() {
   print "%B%(!.%F{red}.%F{green})%n@${host}"
 }
 
+prompt_git_dirty () {
+  [[ "$(git rev-parse --is-inside-work-tree)" == "true" && \
+     -n "$(git status --porcelain --ignore-submodules)" ]]
+}
+
 rprompt_git() {
   ref=${vcs_info_msg_0_}
   if [[ -n ${ref} ]]; then
-    if test -n "$(git status --porcelain --ignore-submodules)"; then
+    if prompt_git_dirty; then
         print '%F{yellow}'$GIT_DIRTY_CHAR'%f'
     fi
   fi
@@ -37,12 +42,9 @@ rprompt_git() {
 # Git: branch/detached head, dirty status
 prompt_git() {
   local color ref
-  is_dirty() {
-    test -n "$(git status --porcelain --ignore-submodules)"
-  }
   ref=${vcs_info_msg_0_}
   if [[ -n ${ref} ]]; then
-    if is_dirty; then
+    if prompt_git_dirty; then
       color=yellow
     else
       color=green