Call for zchunk repodata testers

[Jonathan Dieter]

Just a heads up Rawhide has had zchunked metadata for almost three
weeks, and I'd greatly appreciate some more testing on the client side
before we finish pushing the client changes to Rawhide.

If you're running Rawhide, are willing to test, and have backups of
libdnf and librepo, please enable the COPR by running:

dnf copr enable jdieter/dnf-zchunk
dnf update librepo libdnf

At this point all tools using libdnf will default to zchunked metadata
if it's available.

If the second day's repository download size for Rawhide is less than
54MB, you'll know everything's working correctly.

--- Details, feel free to ignore ---

I've been testing it on Rawhide for the last three weeks or so, and the
minimum I've downloaded has been about 1.2MB (updating every day),
while the max today was about 7.9MB (haven't updated for over a week). 
So far, I haven't hit any bugs, but I've only been regularly testing
DNF in the terminal.  I did do initial testing with PackageKit and
microdnf, and they worked fine too.

Currently only primary.xml, filelists.xml and other.xml are zchunked,
but I've just finished extending zchunk support to all metadata types
in createrepo_c, and the changes should be making their way to Rawhide
sometime in the not-to-distant future.

Again, a huge thank you to everyone who's helped with this, and
especially to Daniel Mach for reviewing the large invasive patches
required to make all this work, Neal Gompa for helping push this
change, and Kevin Fenzi for flipping the switch to start generating
zchunked metadata in Rawhide.

Jonathan