use loop for option handling

gentooup.sh

@@ -39,15 +39,27 @@ if [ "$(stat -c %d:%i /)" != "$(stat -c %d:%i /proc/1/root/.)" ]; then
   CHROOTED=1
 fi
 
-if [[  ${1} == "--no-sync" || ${2} == "--no-sync" ]] ; then
-  echo "not syncing"
-  SYNC_COMMAND=""
-fi
-
-if [[  ${1} == "--full" || ${2} == "--full" ]] ; then
-  echo "Do a full upgrade including build dependencies"
-  PORTAGE_UPGRADE_OPTIONS+=("--with-bdeps=y")
-fi
+while [[ $# -gt 0 ]]; do
+    case $1 in
+      --no-sync)
+        echo "not syncing"
+        SYNC_COMMAND=""
+        shift
+        ;;
+      --full)
+        echo "Do a full upgrade including build dependencies"
+        PORTAGE_UPGRADE_OPTIONS+=("--with-bdeps=y")
+        shift
+        ;;
+      --*)
+        echo "Unknown option $1"
+        shift
+        ;;
+      *)
+        echo "Positional arguments aren't supported"
+        ;;
+    esac
+  done
 
 if [[ $CHROOTED == 1 ]] ; then
   SYNC_COMMAND="layman -S"