architecture wildcards, type-handling, etc.

[Peter Eisentraut <petere@debian.org>]

Since etch, dpkg has supported architecture wildcards such as "linux-any" and 
"any-powerpc", which can, among other things, be used to express Linux-only 
build dependencies like this:

Build-Depends: libcap2-dev [linux-any]

instead of one of the previous approaches:

Build-Depends: libcap2-dev | not+linux-gnu	# works, but not documented(?)

or using type-handling to expand the wildcard manually:

Build-Depends: libcap2-dev [alpha amd64 arm armeb armel hppa i386 ia64 lpia 
m32r m68k mips mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb sparc]

The latter two approaches have obvious flaws, but it seems that no one is using 
the built-in dpkg approach.  Is there anything wrong with it?  Are people just 
not aware of it?

Partial answer: pbuilder doesn't support that style yet, so you can't build 
packages that way (bug #363193).

Comments?