"dpkg-buildpackage -b" and "dpkg-source --before-build"

[Jonathan Nieder <jrnieder@gmail.com>]

Hi Raphaël,

Trying to build a package of format 3.0 (quilt) with the
upstream tarball missing, I get errors:

 $ debuild -I -i -b
  dpkg-buildpackage -rfakeroot -D -us -uc -I -i -b
 [...]
  dpkg-source -I -i --before-build csound
 dpkg-buildpackage: host architecture i386
 dpkg-source: error: can't build with source format '3.0 (quilt)': no orig.tar file found

As I understand it, the problem is this:

 - before building, people want dpkg-buildpackage to make sure
   all patches are applied for them

 - this requires looking at the source package

 - there is no source package

Personally, I am not sure about that first step: shouldn’t
dpkg-buildpackage just build whatever it is presented with, leaving
the unpack and build processes entirely independent?  In other words,
I wish the facility to call --before-build were optional.

But I am open to other solutions, too.  Thoughts?
Jonathan