Update report:
===========
Downloaded xdelta3 source code from:
and build it locally with
unxz xdelta3-3.0.8.tar.xz
tar xf xdelta3-3.0.8.tar
cd xdelta3-3.0.8/
./configure --prefix=/home/ibanez/local
mkdir ~/local
make -j8
make install
Then rerun the self-comparison test:
~/local/bin/xdelta3 -s luisrecreated2.tar luisrecreated2.tar delta3
and got:
10189 bytes delta3
Which is a reasonably small file, for the output of a self-comparison.
Then run the initial comparison of the tar file generated by
git-buildpackage vs the upstream tar, as
~/local/bin/xdelta3 -s luisrecreated2.tar tarball.tar delta4
and got a more reasonable output this time:
979838 bytes delta4
So, it looks like, xdelta version 3 has addressed the problem.
However the syntax of its options have changed.
(see the -s flag instead of the previous "delta" sub-command).
What do we do ?
=============
I could generated the delta with xdelta3 and populate the
pristine-tar branch, but, it is unclear whether this will do
any good if the other systems that will attempt to build
the package are still using xdelta 1.1.3.
Suggestion A:
===========
From reading the gbp.conf man page:
It seems that we could put a customized gbp.conf file in this specific
repository, by placing it in:
debian/gbp.conf : per repository/branch configuration
To change the default behavior and exclude the use of pristine-tar
(and hence the downstream use of xdelta), by using the setting:
[DEFAULT]
pristine-tar = False
The justification would be that:
xdelta 1.1.3 in sid, has limitation to files smaller than 2Gb,
and our tar file is 2.9Gb
Another option would be to change "pristine-tar" to not use the line 545:
my $ret=system("$xdelta_program delta -0 --pristine $recreatetarball $tarball $delta{delta}")
but use instead:
my $ret=system("$xdelta_program delta -9 --pristine $recreatetarball $tarball $delta{delta}")
(or something along those lines) to trigger the use of compression,
and to make it compare tar files in their compressed form, instead
of their uncompressed one.
This probably would have to be brought to the maintainers of pristine-tar...