address pr comment

src/main/java/com/google/devtools/build/docgen/templates/attributes/common/tags.html

@@ -35,6 +35,8 @@
     cached remotely (but it may be cached locally; it may also be executed remotely).
     Note: for the purposes of this tag, the disk-cache is considered a local cache, whereas
     the http and gRPC caches are considered remote.
+    If a combined cache is specified (i.e. a cache with local and remote components),
+    it's treated as a remote cache and disabled entirely.
   </li>
 
   <li><code>no-remote-exec</code> keyword results in the action or test never being

src/main/java/com/google/devtools/build/lib/remote/RemoteSpawnCache.java

@@ -295,6 +295,6 @@ private void report(Event evt) {
   }
 
   private boolean isRemoteCache(RemoteOptions options) {
-    return !(options.diskCache != null && !options.diskCache.isEmpty());
+    return !isNullOrEmpty(options.remoteCache);
   }
 }