Move the local variable to the else branch so that you don't do an unnecessary substitution

gitprompt.sh

@@ -497,10 +497,11 @@ function updatePrompt() {
   fi
 
   export GIT_UPSTREAM="${git_status_fields[2]}"
-  local GIT_FORMATTED_UPSTREAM="${GIT_PROMPT_UPSTREAM//_UPSTREAM_/\$GIT_UPSTREAM}"
   if [[ -z "${__GIT_PROMPT_SHOW_UPSTREAM}" || "^" == "$GIT_UPSTREAM" ]]; then
     unset GIT_UPSTREAM
     unset GIT_FORMATTED_UPSTREAM
+  else
+    local GIT_FORMATTED_UPSTREAM="${GIT_PROMPT_UPSTREAM//_UPSTREAM_/\$GIT_UPSTREAM}"
   fi
 
   local GIT_STAGED=${git_status_fields[3]}