I cannot find it anywhere in rpm codebase.
The current status section of the proposal describes this as pending two PRs, and in the
dependencies list, they're enumerated. Most of the code is in
https://github.com/malmond77/rpm/tree/cow and enabled through work in
https://github.com/malmond77/librepo/tree/transcode_cow
Hmm, I, personally, see much better perfomance (and storage)
improvements in enabling %_minimize_writes
however there is still
https://bugzilla.redhat.com/show_bug.cgi?id=1872141 to be resolved
before this got enabled by default.
I'm curious about this so I'll look at it, but at first glance it seems tangential
to this proposal.
Thanks, Matthew.