Misc: compton-trans: Allow reading opacity from positional arguments

- compton-trans: Allow reading opacity value from positional arguments,
  like the version in master branch.

- compton-trans: Quit when meeting an unrecognized option.

bin/compton-trans

@@ -26,6 +26,7 @@ opacity=
 cur=
 i=
 
+# Read options
 while getopts "scn:w:o:" option; do
   case "$option" in
     s) wprefix=''; window='' ;;
@@ -37,9 +38,14 @@ while getopts "scn:w:o:" option; do
     n) wprefix='-name '; window="$OPTARG" ;;
     w) wprefix='-id '; window="$OPTARG" ;;
     o) opacity="$OPTARG" ;;
+    \?) exit 1;;
   esac
 done
 
+# Read positional arguments
+shift $(($OPTIND - 1))
+[ -n "$1" ] && opacity="$1"
+
 # Validate opacity value
 if [ -z "$opacity" ]; then
 	echo "No opacity specified."