Bug#368055: debian-policy: Add a section about 'transitional packages'

[Christoph Haas <haas@debian.org>]

Package: debian-policy
Severity: wishlist

Since I just accidentally created a grave bug due to errors in a
transitional package I would like to propose the policy mentions them.

Section 7.5.2 of the policy deals with virtual packages already.
Somewhere near that section I would like to learn about transitional
packages. Quick proposal:

 Sometimes a package A unites functionality from a second package B
 making B obsolete. In this situation the package B becomes a
 'transitional package' that is just needed to move users to the package
 A.

 This is done by removing all files from the package B and setting
 the dependencies as follows:

 A:

 Replaces: B
 Conflicts: B

 B:

 Depends: A
 Description: Transitional package for A
  This is a transitional package which ensures users of B will use
  A in the future. It can safely be removed.

 Is it important that B is not just removed. Even the "Replaces: B" in
 package A is not sufficient for an automatic migration.
 [Even though 'aptitude' already seems to support that.]
 B can be safely removed after the next stable release.

(Note: I'm not sure whether the "Provides: B" is actually necessary. It
works without it. And I understand it that "Provides:" is mainly/only
there for virtual packages.)

Kindly
 Christoph

-- System Information:
Debian Release: 3.1
Architecture: i386 (i686)
Kernel: Linux 2.6.10
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)