Inform about stale information about replacement objects

SHORTCOMINGS.md

@@ -25,6 +25,10 @@ This file is for tracking features that are less well implemented or less powerf
 * **Objects larger than 32 bits cannot be loaded on 32 bit systems**
     * in-memory representations objects cannot handle objects greater than the amount of addressable memory.
     * This will not affect git LFS though.
+
+### `gix`
+
+* object replacements are read once upon opening the repository from their refs and changes to these won't be picked up.
 
 ### `gix-url`