Bug#968226: Build-Depends-If-Available

[Russ Allbery <rra@debian.org>]

Wouter Verhelst <wouter@debian.org> writes:

> -policy: this is a question that has come up before
> (https://lists.debian.org/debian-devel/2016/12/msg00470.html is another
> example that springs to mind, but I'm pretty sure there are more), so I
> think we should document in Policy that a) buildd only looks at the
> first dependency in alternative build-dependencies, and b) why this is
> the case.

Policy already says:
    
    While Build-Depends, Build-Depends-Indep and Build-Depends-Arch permit
    the use of alternative dependencies, these are not normally used by
    the Debian autobuilders. To avoid inconsistency between repeated
    builds of a package, the autobuilders will default to selecting the
    first alternative, after reducing any architecture-specific
    restrictions for the build architecture in question. While this may
    limit the usefulness of alternatives in a single release, they can
    still be used to provide flexibility in building the same package
    across multiple distributions or releases, where a particular
    dependency is met by differently named packages.

in 7.1.  However, it's hidden in a footnote.  Perhaps we should make it
more prominant (and make it clear that it's normative), and tweak the
wording.

-- 
Russ Allbery (rra@debian.org)              <https://www.eyrie.org/~eagle/>