Bug#379630: circular dependencies, improved guarantees

[Ian Jackson <ian@davenant.greenend.org.uk>]

Package: debian-policy

,----[ § 7.2 ]
|      In case of circular dependencies, since installation or removal order
|      honoring the dependency order can't be established, dependency loops
|      are broken at some random point, and some packages may not be able to
|      rely on their dependencies being present when being installed or
|      removed, depending on which side of the break of the circular dependcy
|      loop they happen to be on.
`----

In fact, dpkg will try to break the cycle at a package without a
postinst script.  And the word `random' is wrong; `arbitrary' is more
accurate.  I suggest this wording instead:

      In case of circular dependencies, since installation or removal
      order honoring the dependency order can't be established,
      dependency loops are broken at some arbitrary point, and some
      packages may not be able to rely on their dependencies being
      present when being installed or removed, depending on which side
      of the break of the circular dependcy loop they happen to be on.
      If one of the packages in the loop has no postinst script, then
      the cycle will be broken at that package, so as to ensure that
      all postinst scripts run with the dependencies properly
      configured if this is possible.

Ian.