apt preferences and apt-build's "Archive" line

[Adam Porter <adam@alphapapa.net>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Here is a strange problem:


$ cat /var/cache/apt-build/repository/Release
Archive: apt-build
Component: main
Origin: apt-build
Label: apt-build
Architecture: i386


$ cat /etc/apt/preferences
Package: *
Pin: release a=apt-build
Pin-Priority: 900

Package: *
Pin: release o=""
Pin-Priority: 900

Package: *
Pin: release a=testing
Pin-Priority: 900

Package: *
Pin: release a=unstable
Pin-Priority: 800


$ apt-cache policy nvidia-glx
nvidia-glx:
  Installed: 1.0.8774-3
  Candidate: 1.0.8774-3
  Version table:
 *** 1.0.8774-3 0
        500 file: apt-build/main Packages
     1.0.8774-3 0
        800 http://ftp.us.debian.org unstable/non-free Packages


Now if I change this line in the preferences file:

Pin: release a=apt-build

to:

Pin: release o=apt-build

then we get:

$ apt-cache policy nvidia-glx
nvidia-glx:
  Installed: 1.0.8774-3
  Candidate: 1.0.8774-3
  Version table:
 *** 1.0.8774-3 0
        900 file: apt-build/main Packages
     1.0.8774-3 0
        800 http://ftp.us.debian.org unstable/non-free Packages


Now apt is preferring the version in the apt-build repository.  But why
doesn't pinning by Archive work?  You can see in the apt-build Release file
that the Archive is "apt-build".

This has been bugging me for a long time, and I just discovered that
switching the preference to the Origin works.  But why doesn't the Archive
work?

Is this a bug?  If so, which package should I file it on?  (apt-build is
hardly developed anymore.)
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (GNU/Linux)

iD8DBQFFF4Hh5+GdyTDsrJsRAh5TAJ9DYGNiaBNrH6w4ArMK14FZ0jKuJgCgwqnM
GzkcvDLzGdvvGzoFlkq8RXE=
=nr+X
-----END PGP SIGNATURE-----