[Rpm-ecosystem] Zchunk update

[Jonathan Dieter]

I've released zchunk-0.4.0 which has the last (hopefully) backwards-
incompatible file format change.  Files created by zchunk < 0.4.0 will
be unreadable by 0.4.0+.

Zchunk 0.4.0 now has four bytes of flags, so, barring any bone-headed
disasters in the file format, any further file format changes will be
backwards-compatible.

The latest release is available here:
https://github.com/jdieter/zchunk/archive/0.4.0.tar.gz

The file format is documented here:
https://github.com/jdieter/zchunk/blob/master/zchunk_format.txt

A copr with the latest release (and zchunk-enabled createrepo_c) is
here:
https://copr.fedorainfracloud.org/coprs/jdieter/zchunk

My next step is to add zchunk support to librepo.

A quick summary of the features I wanted to add:
On Mon, 2018-04-16 at 15:47 +0300, Jonathan Dieter wrote:
>  * A python API

Still needs to be done.

>  * GPG signatures in addition to (possibly replacing) overall data
>    checksum

Signatures have now been added to the file format in addition to the
overall checksum.  The current implementation can't actually read or
add a signature, though.

>  * An expiry field? (I'm obviously thinking about signed repodata here)

As per feedback, this isn't necessary.

>  * Tests
>  * More tests

The framework is in place for this, and I have added a single test
case.  More to come.

>  * Other arch testing (it's currently only tested on x86_64)

I've built and tested on ARM, ppc64le, i686 and x86_64 and everything
seems to be working just fine.  I have not yet tested on aarch64.


Jonathan