common/travis/changed_templates.sh: change branch age check for treeless

small logic change because we now have the complete commit history instead
of just `--depth=200`. This preserves the 200 commit limit with a slightly-
enhanced error message (wording clarified and it now shows up as an error
annotation)

common/travis/changed_templates.sh

@@ -10,9 +10,10 @@ case "$tip" in
 	*)         tip="${tip%% *}" ;;
 esac
 
-base="$(git merge-base FETCH_HEAD "$tip")" || {
-	echo "Your branches is based on too old copy."
-	echo "Please rebase to newest copy."
+base="$(git merge-base FETCH_HEAD "$tip")"
+
+[ $(git rev-list --count "$tip" "^$base") -lt 200 ] || {
+	echo "::error title=Branch out of date::Your branch is too out of date. Please rebase on upstream and force-push."
 	exit 1
 }