New approach to obsolete packages

[Richard Braakman <dark@xs4all.nl>]

We've had a number of cases now where it would be convenient to have a
package that removes itself after successful installation.  In some
cases we actually built one (xbase, miscutils), with others we found
another solution (modutils), and with some we don't have a solution
yet (xfnt*).

I think a general solution might be to add a single new dpkg flag:

Self-Destruct: Yes

This tells dpkg to automatically remove the package if nothing else
depends on it.

Packages can start using the flag fight away.  We could make a special
section "obsolete" for them.  Suppose that support for flag gets added
to dpkg 1.5.0.  As soon as the user installs dpkg 1.5.0, all the
obsolete packages get cleaned up nicely.  (Until then, the packages
will hang around with a note saying they're obsolete and can be removed.
No big deal, IMHO.)

I expect that this will be much easier to implement than a generalized
"Supersedes" field.  If you disagree, feel free to prove me wrong :-)

Unfortunately it still does not solve the "base" case.  I don't think
anything short of direct manipulation of dpkg's database can solve that.

Richard Braakman