Make add-remote use title from summary

When we add a remote, load the summary from the repository, and
use the title if there is one. This at the same time serves as
(minimal) validation of the repository url.

xdg-app-builtins-add-remote.c

@@ -7,6 +7,7 @@
 #include "libgsystem.h"
 
 #include "xdg-app-builtins.h"
+#include "xdg-app-utils.h"
 
 static gboolean opt_no_gpg_verify;
 static gboolean opt_if_not_exists;
@@ -26,6 +27,8 @@ xdg_app_builtin_add_remote (int argc, char **argv, GCancellable *cancellable, GE
   gboolean ret = FALSE;
   gs_unref_object XdgAppDir *dir = NULL;
   gs_unref_variant_builder GVariantBuilder *optbuilder = NULL;
+  gs_unref_hashtable GHashTable *refs = NULL;
+  gs_free char *title = NULL;
   const char *remote_name;
   const char *remote_url;
 
@@ -45,14 +48,24 @@ xdg_app_builtin_add_remote (int argc, char **argv, GCancellable *cancellable, GE
 
   optbuilder = g_variant_builder_new (G_VARIANT_TYPE ("a{sv}"));
 
+  if (!ostree_repo_load_summary (remote_url, &refs, &title, cancellable, error))
+    goto out;
+
   if (opt_no_gpg_verify)
     g_variant_builder_add (optbuilder, "{s@v}",
                            "gpg-verify",
                            g_variant_new_variant (g_variant_new_boolean (FALSE)));
+
   if (opt_title)
+    {
+      g_free (title);
+      title = g_strdup (opt_title);
+    }
+
+  if (title)
     g_variant_builder_add (optbuilder, "{s@v}",
                            "xa.title",
-                           g_variant_new_variant (g_variant_new_string (opt_title)));
+                           g_variant_new_variant (g_variant_new_string (title)));
 
   if (!ostree_repo_remote_change (xdg_app_dir_get_repo (dir), NULL,
                                   opt_if_not_exists ? OSTREE_REPO_REMOTE_CHANGE_ADD_IF_NOT_EXISTS :