lib/pull: Add debug message when loading summary from cache

This helps when debugging issues with the cached summary handling.

Closes: #1698
Approved by: cgwalters

src/libostree/ostree-repo-pull.c

@@ -3986,7 +3986,10 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
       goto out;
 
     if (bytes_summary)
-      summary_from_cache = TRUE;
+      {
+        g_debug ("Loaded %s summary from cache", remote_name_or_baseurl);
+        summary_from_cache = TRUE;
+      }
 
     if (!pull_data->summary && !bytes_summary)
       {