Bug#1418: elv-vi shouldn't update-alternatives --remove when upgrading

[Ian Jackson <iwj10@cus.cam.ac.uk>]

Package: elv-vi
Version: 1.8pl4-15

 Preparing to replace elv-vi (using ./editors/elv-vi-1.8pl4-15.deb) ...
 Checking available versions of vi, updating links in /etc/alternatives ...
 Leaving vi (/usr/bin/vi) pointing to /usr/bin/nvi.
 Leaving vi.1 (/usr/man/man1/vi.1) pointing to /usr/man/man1/nvi.1.
 Checking available versions of ex, updating links in /etc/alternatives ...
 Leaving ex (/usr/bin/ex) pointing to /usr/bin/nex.
 Leaving ex.1 (/usr/man/man1/ex.1) pointing to /usr/man/man1/nex.1.
 Checking available versions of view, updating links in /etc/alternatives ...
 Discarding obsolete slave link view.1 (/usr/man/man1/view.1).
 Last package providing view (/usr/bin/view) removed, deleting it.
 Checking available versions of input, updating links in /etc/alternatives ...
 Discarding obsolete slave link input.1 (/usr/man/man1/input.1).
 Last package providing input (/usr/bin/input) removed, deleting it.
 Unpacking replacement elv-vi ...

There is no point calling update-alternatives to remove the links if
you're just upgrading the package.  You should put

if [ $1 != "upgrade" ]
then
  update-alternatives --remove vi /usr/bin/vim
fi

around the relevant parts of the prerm.

Ian.