udevadm-test: allow to specify extra directories to load udev rules files

This adds -D/--extra-rules-dir=DIR switch for 'udevadm test' command.
When specified, udev rules files in the specified directory will be also
loaded. This may be useful for debugging udev rules by copying some udev
rules files to a temporary directory.

shell-completion/bash/udevadm

@@ -70,7 +70,7 @@ _udevadm() {
         [MONITOR_STANDALONE]='-k --kernel -u --udev -p --property'
         [MONITOR_ARG]='-s --subsystem-match -t --tag-match'
         [TEST_STANDALONE]='-v --verbose'
-        [TEST_ARG]='-a --action -N --resolve-names'
+        [TEST_ARG]='-a --action -N --resolve-names -D --extra-rules-dir'
         [TEST_BUILTIN]='-a --action'
         [VERIFY]='-N --resolve-names --root --no-summary --no-style'
         [WAIT]='-t --timeout --initialized=no --removed --settle'
@@ -228,6 +228,9 @@ _udevadm() {
                     -N|--resolve-names)
                         comps='early late never'
                         ;;
+                    -D|--extra-rules-dir)
+                        comps=''
+                        compopt -o dirnames
                 esac
             elif [[ $cur = -* ]]; then
                 comps="${OPTS[COMMON]} ${OPTS[TEST_ARG]} ${OPTS[TEST_STANDALONE]}"