dpkg-source cause gap-atlasrep to FTBFS for no reason

[Bill Allombert <ballombe@debian.org>]

reassign 971203 dpkg-dev
severity grave
retitle dpkg-source cause gap-atlasrep to FTBFS
quit
On Sun, Sep 27, 2020 at 08:58:00PM +0200, Lucas Nussbaum wrote:
> Source: gap-atlasrep
> Version: 2.1.0-2
> Severity: serious
> Justification: FTBFS on amd64
> Tags: bullseye sid ftbfs
> Usertags: ftbfs-20200926 ftbfs-bullseye
> 
> Hi,
> 
> During a rebuild of all packages in sid, your package failed to build
> on amd64.
> 
> > dpkg-source: error: pathname '/<<PKGBUILDDIR>>/debian/gaproot/pkg/AtlasRep' points outside source root (to '/<<PKGBUILDDIR>>')

Dear Dpkg developers,

$ apt-get source gap-atlasrep
Fetched 1351 kB in 2s (722 kB/s)
dpkg-source: info: extracting gap-atlasrep in gap-atlasrep-2.1.0
dpkg-source: info: unpacking gap-atlasrep_2.1.0.orig.tar.bz2
dpkg-source: info: unpacking gap-atlasrep_2.1.0-2.debian.tar.xz
dpkg-source: info: using patch list from debian/patches/series
dpkg-source: info: applying doc-makefile
dpkg-source: info: applying default-dir
dpkg-source: error: pathname
'gap-atlasrep-2.1.0/debian/gaproot/pkg/AtlasRep' points outside source
root (to '/tmp/gap-atlasrep-2.1.0')
E: Unpack command 'dpkg-source --no-check -x gap-atlasrep_2.1.0-2.dsc'
failed.

There is no rationale to reject such a symlink which does not point
_outside_ the source root, but _to_ the source root.
This leads to a spurious FTBFS.

Also I am concerned that developers might need to unpack old packages
with symlinks in them. There should be a way to do it, if only to fix
the packaging.

Cheers,
Bill