Package: pristine-tar
Version: 1.33
Severity: important
(This bug may be a duplicate of other ones filed against pristine-tar; I
haven't yet investigated their cause.)
pristine-tar seems not to know how to efficiently re-compress files
compressed by gzip --rsyncable on both Jessie and Sid (which have gzip
1.6-4). From a Sid chroot:
$ gunzip pristine-tar_1.33.tar.gz
$ gzip --rsyncable pristine-tar_1.33.tar
$ pristine-tar gendelta pristine-tar_1.33.tar.gz tmp
warning: pristine-gz cannot reproduce build of pristine-tar_1.33.tar.gz;
storing 80% size diff in delta
(Please consider filing a bug report so the delta size can be improved.)
No such error happens if you leave off --rsyncable.
In fact, this happens on the unmodified tarball of pristine-tar itself
(versions 1.31, 1.32, and 1.33, but not older versions):
$ apt-get source --download-only pristine-tar
$ pristine-tar gendelta pristine-tar_1.33.tar.gz tmp
warning: pristine-gz cannot reproduce build of pristine-tar_1.33.tar.gz;
storing 86% size diff in delta
(Please consider filing a bug report so the delta size can be improved.)
I noticed this because uscan's repack mode calls mk-origtargz, which uses
Debhelper::Compression, which uses Dpkg::Compression, which passes
--rsyncable by default. From /usr/lib/perl5/Dpkg/Compression.pm:
gzip => {
file_ext => 'gz',
comp_prog => [ 'gzip', '--no-name', '--rsyncable' ],
decomp_prog => [ 'gunzip' ],
default_level => 9,
},
So I bet this affects a number of packages. For instance, this is how
pristine-tar's own native tarballs were made:
$ gunzip < pristine-tar_1.33.tar.gz | gzip -9 --no-name --rsyncable | diff -s -
pristine-tar_1.33.tar.gz
Files - and pristine-tar_1.33.tar.gz are identical
The changelog entry for pristine-tar 1.14 (August 2011) implies that it's
supposed to support the --rsyncable option already, but perhaps since
then, the gzip format has changed.
--
Geoffrey Thomas
https://ldpreload.com
[email protected]
