I think you're talking about commit be9e7056daaf9112afc394fea96fe3fe67b26070.
That code is from David Ponce:
2003-04-27 David Ponce <
david@dponce.com>
* recentf.el
Major rewrite. The code is reordered, cleaner and faster.
Introduce new options to automatically cleanup the recent list,
and to handle filename transformation (for example to use true
filenames).
I imagine I did commit it in the old CVS.