Orphaning deltarpm

[Jonathan Dieter]

Hi everyone,

I'm orphaning deltarpm because, as it's currently used in Fedora, it's
not very effective, bugs keep getting opened against it because it's
not working as well as it should (mostly an infra issue as opposed to a
problem with the tool itself), and I no longer have the time or
motivation to deal with these tickets when it seems like there's not
much benefit.

The main problem with deltarpms is that we don't keep them from compose
to compose, so we're only getting the previous day's deltarpms when we
download updates.  This means that the only way you'll be able to truly
take advantage of deltarpms is if you get updates after every compose.

For more details, see:
https://pagure.io/releng/issue/7215

Bugs that need to be looked into:

https://bugzilla.redhat.com/show_bug.cgi?id=1873876 - This is mostly
two different problems: 1) when the zstd algorithm changes, deltarpms
cannot be rebuilt to the exact same RPM, and 2) deltarpms for the
kernel package seem to be impossible to rebuild to the exact same RPM
due to the compression format used on the kernel RPMs

https://bugzilla.redhat.com/show_bug.cgi?id=2058477 - No idea why 100+
MB of packages failed to build correctly (no logs in the ticket), but
it's probably related to (1) above.

A brief history of how deltarpms came to be added to Fedora:
https://www.jdieter.net/posts/2013/05/31/eulogy-for-yum-presto/

Finally, I want to say a huge thank you to Michael Schroeder, who wrote
deltarpm.  The tool itself still works beautifully well, and the issues
we're seeing are all infrastructure related.  I also want to say thank
you to everyone who worked on getting deltarpms into Fedora in the
first place and who have helped keep them running this long.

Jonathan