Upgrading pristine-xz on jubany

[Vincent Ladeuil]

Some good news after my tests Friday and this week-end:

>>>>> Vincent Ladeuil <vila+udd at canonical.com> writes:

<snip/>

    > - I got in touch with xz maintainers and a fix is on its way there
    > (many thanks to Lasse Collin for its invaluable help here). This
    > will require an additional fix to pristine-xz which I will submit
    > as soon as I can test the xz fix).

Lasse Collin gave me a patch that I tested successfully: 135 out the 150
failures are fixed.

    > And don't forget that when a package fail to import one release,
    > all the subsequent ones are blocked as well. When we fixed the
    > bzip2 issue last January, ~70 packages were blocked accounting for
    > ~800 releases (don't quote on these numbers, it's just a vague
    > remembering but the scales should be ok).

<cough> 135 packages were blocking 4437 releases here \o/ So the scale
is even bigger than I thought.

The fix has not been committed upstream yet[1] so we'll need to carry it
ourselves.

Merge proposal/patch submission time ;)

I'll followup with more explanations about the root cause later.

   Vincent

[1]: In order to re-create the compressed file, one has to provide xz
with a list of block sizes. Since this is a feature that only a handful
of use cases will benefit from, it will need to be cooked a bit before
landing in xz-utils. I had a deep enough discussion with Lasse to be
confident that the feature will find its way into an upcoming release in
one form or another but until this happen, we'll need to carry a patch
in both xz-utils and pristine-tar. But I don't expect significant
changes except for the option name (which is why I can't send the full
patch to pristine-tar for now).