Bug#824495: debian-policy: Source packages "can" declare relationships

[Santiago Vila <sanvila@unex.es>]

Package: debian-policy
Severity: wishlist

Hello.

Policy 7.7 says: (Bold in "can" is mine)

  Source packages that require certain binary packages to be installed
  or absent at the time of building the package *can* declare
  relationships to those binary packages.

I interpret this "can" in the sense that this is the vocabulary that
the maintainer is allowed to use when writing control files.

To my surprise, however, today a maintainer has quoted this "can" word
as a rationale for a missing Build-Conflicts not to be a bug of serious
severity:

  "No _must_ directive here. It is not a Policy violation if you don't
  use Build-Conflicts."

If my idea that policy is just describing the vocabulary is close to
reality, I would perhaps suggest something like this:

  The following relationsips are available for source packages to
  express the fact that they require certain binary packages to be
  installed or absent at the time of building the package.

but then it would be nice to state somewhere later that Build-Depends
and Build-Conflicts are not just "optional" but mandatory when the
referenced packages are either required to be present or required to
be absent.


While we are at it, I understand, because it would involve a huge
amount of computation to determine, that we can't test every package
against every other binary package to discover undeclared
build-conflicts.

Is there any rule to decide what to put in build-conflicts?

Thanks.