Did your test was similar to this?

<pre>
$ pwd

$ fossil di
---
+++
@@ -537,11 +537,11 @@
   }

   if( nFull<=n || memcmp(g.zLocalRoot, zFull, n) ){
     blob_reset(&full);
     if( errFatal ){
-      fossil_fatal("file outside of checkout tree: %s", zOrigName);
+      fossil_fatal("file outside of checkout tree: zLocalRoot: zFull: zOrigName, g.zLocalRoot, zFull);
     }
     return 0;
   }
   blob_append(pOut, &zFull[n], nFull-n);
   return 1;
</pre>

It seems to work for me..