Merge remote-tracking branch 'origin/pr/93'

* origin/pr/93:
  qubes-dom0-update: print message when updates are available
  qubes-dom0-update: do not attempt to install updates with --check-only
  qubes-dom0-update: Pass --check-only option to the updatevm too

dom0-updates/qubes-dom0-update

@@ -82,6 +82,7 @@ while [ $# -gt 0 ]; do
             ;;
         --check-only)
             CHECK_ONLY=1
+            UPDATEVM_OPTS+=( "$1" )
             ;;
         --preserve-terminal)
             exit_cmd=
@@ -136,6 +137,10 @@ case ${YUM_ACTION=upgrade} in
     ;;
 esac
 
+if [ "$CHECK_ONLY" == "1" ]; then
+    REMOTE_ONLY=1
+fi
+
 # Redirect operations on templates to qvm-template command
 if find_regex_in_args '^qubes-template-' "${PKGS[@]}"; then
     if [[ ${#PKGS[@]} -ne 1 ]]; then
@@ -270,6 +275,15 @@ qvm-run "${QVMRUN_OPTS[@]}" -- "$UPDATEVM" "$CMD" < /dev/null
 
 RETCODE=$?
 if [[ "$REMOTE_ONLY" = '1' ]] || [ "$RETCODE" -ne 0 ]; then
+    if [ "$CHECK_ONLY" = '1' ]; then
+        if [ "$RETCODE" -eq 100 ]; then
+            echo "There are dom0 updates available" >&2
+        elif [ "$RETCODE" -eq 0 ]; then
+            echo "No dom0 updates available" >&2
+        else
+            echo "Failed to check for dom0 updates" >&2
+        fi
+    fi
     exit $RETCODE
 fi
 # Wait for download completed