preventing md5 mismatch errors from compression changes

[Andre Robatino]

Toshio Kuratomi <a.badger <at> gmail.com> writes:

> Commandline xz would compress differently and other random apps that we
> don't know of would as well.  This may not cause any difficulties... OTOH,
> it could be that people *are* depending on the compression being the same.
> breaking that assumption is something we can do at the Fedora release
> boundary... not so easily within a Fedora release.

Fair enough, it's possible (though a little tricky) for people who need the new
compression in F14 and below to use the yum shell procedure to temporarily get
it, then reverse the procedure afterwards. I'll just have to make sure to
document it properly.

> Beyond this, there's the fact that there's not a compelling reason to update
> on F14 and that the present plan for the compat libs package is that it will
> go away before rawhide becomes F15.

What about Fedora testers using deltaisos? (For example see
https://fedorahosted.org/rel-eng/ticket/3575 .) During F15 testing, the deltas
after F15 Alpha TC1 should be functional, but will require anyone using them who
doesn't currently have F15/Rawhide installed to use the yum shell procedure I
outlined, to temporarily get the new compression to apply them. Without the
xz-compat-libs package this won't be possible. Many testers such as myself won't
install F15 on bare metal until Final, and even if they were willing, depending
on the state of Alpha TC1 it may not be installable from that. In addition,
people on F15 and above such as myself who temporarily need the old compression
(for a typical use case see
https://fedorahosted.org/fedora-infrastructure/ticket/2241 ) won't be able to do
this at all. Of course, in both directions there's the option of creating a
virtual guest, but this is FAR more painful (both in speed and bloat) then just
having a tiny xz-compat-libs package, together with temporarily up/downgrading
the deltarpm/deltaiso packages - which doesn't require yum shell.

For these reasons alone, I believe xz-compat-libs should be made available
indefinitely in F15 and above, and provide a copy of liblzma.so.* for each older
version of the compression. Since the package already exists, maintaining it
should be trivial. Obviously it doesn't need to be installed by default, just
available in the repo.