Also handle the abort-upgrade postrm case

When the diversion was added in a particular version of a package,
an aborted upgrade to a newer version with the diversion from an
older version without the diversion should remove the diversion when
rolling back to the older version.  Add the necessary postrm code and
explanation.  Thanks to Raphael Hertzog for the review.

diff --git a/policy.sgml b/policy.sgml
index 127c6a25bffae9661d5d917e1846b08820cacf91..5975d373b35308cf078be0957adeb35a42399b2c 100644 (file)
--- a/policy.sgml
+++ b/policy.sgml
@@ -10577,10 +10577,21 @@ install-info --quiet --remove /usr/share/info/foobar.info
      dpkg-divert --package smailwrapper --remove --rename \
         --divert /usr/sbin/smail.real /usr/sbin/smail
   fi
-       </example> The postrm should not remove the diversion on upgrades
-       both because there's no reason to remove the diversion only to
-       immediately re-add it and since the postrm of the old package is
-       run after unpacking so the removal of the diversion will fail.
+       </example> If the diversion was added at a particular version, the
+       postrm should also handle the failure case of upgrading from an
+       older version (unless the older version is so old that direct
+       upgrades are no longer supported):
+       <example>
+  if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
+     dpkg-divert --package smailwrapper --remove --rename \
+        --divert /usr/sbin/smail.real /usr/sbin/smail
+  fi
+       </example> where <tt>1.02-2</tt> is the version at which the
+       diversion was first added to the package.  The postrm should not
+       remove the diversion on upgrades both because there's no reason to
+       remove the diversion only to immediately re-add it and since the
+       postrm of the old package is run after unpacking so the removal of
+       the diversion will fail.
       </p>
 
       <p>