allow remote add to succeed when offline

Updating the metadata at the end of adding a remote means that it fails
if we're offline, even if we have the .flatpakrepo file available.
Unlike the other error cases in the process, which mean the operation
really has messed up, the remote is actually usable even if the
metadata update fails, because future operations will grab the
summary and any new metadata - so we should change this to a warning
to allow the operation to succeed when we're offline.

https://github.com/flatpak/flatpak/issues/917

app/flatpak-builtins-add-remote.c

@@ -290,6 +290,7 @@ flatpak_builtin_add_remote (int argc, char **argv,
   g_autoptr(GKeyFile) config = NULL;
   g_autoptr(GBytes) gpg_data = NULL;
   gboolean changed = FALSE;
+  g_autoptr(GError) local_error = NULL;
 
   context = g_option_context_new (_("NAME LOCATION - Add a remote repository"));
   g_option_context_set_translation_domain (context, GETTEXT_PACKAGE);
@@ -361,8 +362,23 @@ flatpak_builtin_add_remote (int argc, char **argv,
     return FALSE;
 
   /* We can't retrieve the extra metadata until the remote has been added locally, since
-     ostree_repo_remote_fetch_summary() works with the repository's name, not its URL. */
-  return flatpak_dir_update_remote_configuration (dir, remote_name, cancellable, error);
+     ostree_repo_remote_fetch_summary() works with the repository's name, not its URL.
+     Don't propagate IO failed errors here because we might just be offline - the
+     remote should already be usable. */
+  if (!flatpak_dir_update_remote_configuration (dir, remote_name, cancellable, &local_error))
+    {
+      if (g_error_matches (local_error, G_IO_ERROR, G_IO_ERROR_FAILED))
+        {
+          g_printerr (_("Warning: Could not update extra metadata for '%s': %s\n"), remote_name, local_error->message);
+        }
+      else
+        {
+          g_propagate_error (error, g_steal_pointer (&local_error));
+          return FALSE;
+        }
+    }
+
+  return TRUE;
 }
 
 gboolean