mark front push implementation incomplete

src/vdp_pesi.c

@@ -586,6 +586,13 @@ pesi_buf_bytes(struct req *req, enum vdp_action act, void **priv,
 
 	/*
 	 * check unlocked if an attempt to unpend makes any sense at all
+	 *
+	 * XXX front delivery implementation is incomplete, we would need to
+	 * push the front in other places, too
+	 *
+	 * Yet, as explained in the documentation of the "thread" flag, front
+	 * pushing really does not make much sense, the only case actually is
+	 * non-esi non-gzip uncacheable streaming...
 	 */
 	AN(tree->front);
 	if (pesi->flags & PF_CFG_FRONT_PUSH &&