package versions in dselect, and Release file

[Ian Zimmerman <itz@speakeasy.org>]

What are the packaging frontends (dselect in particular) supposed to
do when 2 sources from sources.list provide different version numbers
of the same package?

I have a potato system, but I downloaded a couple of upgraded packages from
woody and placed them in a local mirror directory.  I generated the
Packages files with dpkg-scanpackages.  That went fine, so I added a
"deb file:" line for the local mirror to sources.list and run
dselect.  In the Select phase I could see the newer versions as
available.  I selected them.  But the Install phase ignored my local
mirror, tried to download the updates from the potato archive, and
failed. 

I noted while dselect was hitting the sources it said something like

deb file:/foo/bar Release Ignored

Of course, I don't have a Release file in the mirror directory.  Is
that necessary for it to be recognized as a worthy source?  If so, how
do I generate one; dpkg-scanpackages doesn't.  Or is there something
else wrong with what I'm trying?

-- 
Ian Zimmerman, Oakland, California, U.S.A.
In his own soul a man bears the source
from which he draws all his sorrows and his joys.
Sophocles.