Bug#1015263: libidn2-0: Depends sgml-base

[Chris Hofstaedtler]

Control: reassign -1 debhelper
Control: found -1 13.7
Control: affects -1 libidn2-0

Hi Niels,

* Simon Josefsson <simon@josefsson.org>:
> Thorsten Glaser <tg@mirbsd.de> writes:
> 
> > A new dependency on sgml-base was introduced to the shared library
> > package, and it’s not documented in the changelog. This raises red
> > flags.
> 
> Hi.  Thanks for the report.  Indeed, this looks strange, and there is no
> modification of the libidn2/debian/ files that would explain this.  It
> seems sgml-base is added via the 'Depends: ${misc:Depends},
> ${shlibs:Depends}' and/or 'Pre-Depends: ${misc:Pre-Depends}' clauses, so
> I guess something changed in 'dh' to cause this new behaviour.  Any
> ideas?

https://salsa.debian.org/debian/debhelper/-/commit/99892be481c1dd06d9866854a2c14e6a70ae12b7
looks suspicious, as it rewrites the addsubstvar function, which is
used by dh_installcatalogs. Indeed if I remove the addsubstvar call
with remove=1 from dh_installcatalogs, sgml-base no longer shows up
in misc:Depends of libidn2-0.

Judging by the current list of `apt-cache rdepends sgml-base`, this
problem has already spread quite a bit.

I think this is a bug in debhelper, and maybe it could be "fixed"
twice:

dh_installcatalogs is not supposed to be idempotent, so the
addsubstvar to "remove the dependency" could just go away?

Then, addsubstvar could maybe also lose its "remove" argument? A
quick codesearch search didn't find me any callers using that, apart
from dh_installcatalogs.

But this is all me typing into a bug report without knowing anything
about debhelper API :-)

Best,
Chris