Improve Startup CSS fail message

- Add important note about CE/EE split
- Increase recommendation to apply
  patch.

scripts/frontend/startup_css/startup_css_changed.sh

@@ -10,10 +10,10 @@ echo "-----------------------------------------------------------"
 startup_glob="*stylesheets/startup*"
 
 echo "Staging changes to '${startup_glob}' so we can check for untracked files..."
-git add ${startup_glob}
+git add "${startup_glob}"
 
-if [ -n "$(git diff HEAD --name-only -- ${startup_glob})" ]; then
-  diff=$(git diff HEAD -- ${startup_glob})
+if [ -n "$(git diff HEAD --name-only -- "${startup_glob}")" ]; then
+  diff=$(git diff HEAD -- "${startup_glob}")
   cat <<EOF
 
 Startup CSS changes detected!
@@ -21,14 +21,19 @@ Startup CSS changes detected!
 It looks like there have been recent changes which require
 regenerating the Startup CSS files.
 
-**What should I do now?**
+IMPORTANT:
 
-IMPORTANT: Please make sure to update your MR title with "[RUN AS-IF-FOSS]" and start a new MR pipeline
+  - If you are making changes to any Startup CSS file, it is very likely that
+    **both** the CE and EE Startup CSS files will need to be updated.
+  - Changing any Startup CSS file will trigger the "as-if-foss" job to also run.
+
+HOW TO FIX:
 
 To fix this job, consider one of the following options:
 
-  1. Regenerating locally with "yarn run generate:startup_css".
-  2. Copy and apply the following diff:
+  1. (Strongly recommended) Copy and apply the diff below:
+  2. Regenerate locally with "yarn run generate:startup_css".
+     You may need to set "FOSS_ONLY=1" if you are trying to generate for CE.
 
 ----- start diff -----
 $diff