feat: default to hosted web-stack repository when no --repository given

tools/spry/Deploy.vala

@@ -19,6 +19,12 @@ namespace Spry.Cli {
      */
     public class Deploy : GLib.Object {
 
+        /**
+         * The default USM repository used when no `--repository` is given:
+         * the hosted web-stack repository on packages.astrologue.nz.
+         */
+        public const string DEFAULT_REPOSITORY = "https://packages.astrologue.nz/repo/web-stack/repo.usmr";
+
         /** `--system fedora` base image ({@link Deploy.resolve_system}). */
         public const string SYSTEM_FEDORA_BASE = "registry.fedoraproject.org/fedora:latest";
 
@@ -131,9 +137,17 @@ namespace Spry.Cli {
                 argv += "--spm";
                 argv += spm;
             }
-            foreach (var repository in repositories) {
+            if (repositories.length > 0) {
+                foreach (var repository in repositories) {
+                    argv += "--repository";
+                    argv += repository;
+                }
+            }
+            else {
+                // No explicit repositories: default to the hosted web-stack
+                // repository so stack dependencies resolve out of the box
                 argv += "--repository";
-                argv += repository;
+                argv += DEFAULT_REPOSITORY;
             }
             if (installer_url != null) {
                 argv += "--installer-url";