scripts/deploy: allow omitting the "host" argument

scripts/sync

@@ -2,9 +2,10 @@
 #!nix-shell -i bash -p bash -p rsync -p sane-scripts.sync-music
 
 usage() {
-  echo "sync [flags ...] <host> [<host> ...] [passthrough flags ...]"
+  echo "sync [flags ...] [<host> [<host> ...]] [passthrough flags ...]"
   echo "where:"
   echo "  host: all|desko|lappy|moby"
+  echo "  - defaults to 'all' if omitted"
   exit 1
 }
 
@@ -100,7 +101,12 @@ parseArgs() {
         ;;
     esac
   done
+
   passthruArgs+=("$@")
+
+  if [[ ${#hosts[@]} -eq 0 ]]; then
+    hosts+=(desko lappy moby)
+  fi
 }
 
 parseArgs "$@"