Re: Debian part of a version number when epoch is bumped

From	Russ Allbery <rra@debian.org>
Newsgroups	linux.debian.devel
Subject	Re: Debian part of a version number when epoch is bumped
Date	2018-02-14 22:00 +0100
Message-ID	<vjcjL-1gD-3@gated-at.bofh.it> (permalink)
References	(6 earlier) <vjaUG-oA-21@gated-at.bofh.it> <vjbxo-Sd-9@gated-at.bofh.it> <vjbH3-Vh-5@gated-at.bofh.it> <vjbQK-YF-5@gated-at.bofh.it> <vjc0p-12Y-1@gated-at.bofh.it>
Organization	The Eyrie

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Michael Stone <mstone@debian.org> writes:

> That doesn't matter. The fundamental problem was that it's impossible to
> predict that a future package would have an older version of the
> software with a newer name. Whether that's done with an epoch that
> (horrors!) won't go away or because someone creates a crazy version
> string that obfuscates what's being done (yay?), the unpredictable
> breakage is the same. The solution isn't to get rid of epochs, the
> solution is to not create packages which contain older versions of
> software with newer names.

Not that this is probably easily fixable at this point, but mulling on
this a bit, I think it's because we actually have two version orderings
that we're compressing into one ordering.

We want to do two things here:

* Give a package a larger version number so that the archive knows that it
  replaces the previous version of the package and so that clients know
  that this package should be installed in preference to the previous
  version.

* Express versioned dependencies in other packages, allowing you to say
  that you need at least version 1.8 of a package and 1.6 will not
  suffice.

These seem like the same thing, but they subtly aren't.  There are times
when we want to tell the archive to replace version 1.8 with 1.6, and tell
all apt clients to install 1.6 in preference to 1.8, but do not want that
package to satisfy a version dependency of >= 1.8.

Since there are two goals, a more correct implementation would be to split
these into two versions.  The simplest would be to have an integer
"version epoch" field in the package metadata separate from the version
number.  So instead of:

Version: 1.8-1

Version: 1:1.6-1

you'd have:

Version: 1.8-1

Version: 1.6-1
Epoch: 1

We then could implement the separate semantics: only the version field
would be used for interpackage dependencies, so 1.6-1 with epoch 1 would
not satisfy >= 1.8 dependencies, but DAK and apt clients would know that
any package with epoch 1 supersedes packages with no epoch for archive and
default installation purposes.

Of course, getting to that from where we are now may be substantially more
trouble than it's worth, and it would necessarily be a very slow rollout
process (and there are still issues with unique filenames).

-- 
Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>

Thread

Debian part of a version number when epoch is bumped Jeremy Bicha <jbicha@debian.org> - 2018-02-05 16:50 +0100
  Re: Debian part of a version number when epoch is bumped Matt Zagrabelny <mzagrabe@d.umn.edu> - 2018-02-05 17:00 +0100
  Re: Debian part of a version number when epoch is bumped Mattia Rizzolo <mattia@debian.org> - 2018-02-05 17:10 +0100
    Re: Debian part of a version number when epoch is bumped Colin Watson <cjwatson@debian.org> - 2018-02-06 09:40 +0100
      Re: Debian part of a version number when epoch is bumped Mattia Rizzolo <mattia@debian.org> - 2018-02-06 14:30 +0100
        Re: Debian part of a version number when epoch is bumped Colin Watson <cjwatson@debian.org> - 2018-02-06 23:30 +0100
          Re: Debian part of a version number when epoch is bumped Michael Stone <mstone@debian.org> - 2018-02-07 13:20 +0100
          Re: Debian part of a version number when epoch is bumped Jonathan McDowell <noodles@earth.li> - 2018-02-07 11:10 +0100
            Re: Debian part of a version number when epoch is bumped Wouter Verhelst <wouter@debian.org> - 2018-02-07 18:00 +0100
          Re: Debian part of a version number when epoch is bumped Seth Arnold <seth.arnold@canonical.com> - 2018-02-08 00:50 +0100
            Re: Debian part of a version number when epoch is bumped Ian Jackson <ijackson@chiark.greenend.org.uk> - 2018-02-09 13:10 +0100
              Re: Debian part of a version number when epoch is bumped Philipp Kern <pkern@debian.org> - 2018-02-09 13:50 +0100
                Re: Debian part of a version number when epoch is bumped Ian Jackson <ijackson@chiark.greenend.org.uk> - 2018-02-09 17:10 +0100
                Re: Debian part of a version number when epoch is bumped Colin Watson <cjwatson@debian.org> - 2018-02-09 18:20 +0100
                Re: Debian part of a version number when epoch is bumped Philipp Kern <pkern@debian.org> - 2018-02-09 18:20 +0100
                Re: Debian part of a version number when epoch is bumped Russ Allbery <rra@debian.org> - 2018-02-09 18:30 +0100
                Re: Debian part of a version number when epoch is bumped Philipp Kern <pkern@debian.org> - 2018-02-09 19:00 +0100
                Re: Debian part of a version number when epoch is bumped Russ Allbery <rra@debian.org> - 2018-02-09 19:20 +0100
                Re: Debian part of a version number when epoch is bumped Andrey Rahmatullin <wrar@debian.org> - 2018-02-09 20:30 +0100
                Re: Debian part of a version number when epoch is bumped Jeremy Bicha <jbicha@debian.org> - 2018-02-09 20:40 +0100
                Re: Debian part of a version number when epoch is bumped Guillem Jover <guillem@debian.org> - 2018-02-12 03:30 +0100
                Re: Debian part of a version number when epoch is bumped Wouter Verhelst <wouter@debian.org> - 2018-02-14 13:00 +0100
                Re: Debian part of a version number when epoch is bumped Vincent Bernat <bernat@debian.org> - 2018-02-14 14:00 +0100
                Re: Debian part of a version number when epoch is bumped Jeremy Bicha <jbicha@ubuntu.com> - 2018-02-14 14:50 +0100
                Re: Debian part of a version number when epoch is bumped Michael Biebl <biebl@debian.org> - 2018-02-14 16:40 +0100
                Re: Debian part of a version number when epoch is bumped Henrique de Moraes Holschuh <hmh@debian.org> - 2018-02-14 15:00 +0100
                Re: Debian part of a version number when epoch is bumped Lars Wirzenius <liw@liw.fi> - 2018-02-14 15:20 +0100
                Re: Debian part of a version number when epoch is bumped Vincent Bernat <bernat@debian.org> - 2018-02-14 19:00 +0100
                Re: Debian part of a version number when epoch is bumped Lars Wirzenius <liw@liw.fi> - 2018-02-14 20:30 +0100
                Re: Debian part of a version number when epoch is bumped Vincent Bernat <bernat@debian.org> - 2018-02-14 21:10 +0100
                Re: Debian part of a version number when epoch is bumped Michael Stone <mstone@debian.org> - 2018-02-14 21:20 +0100
                Re: Debian part of a version number when epoch is bumped Vincent Bernat <bernat@debian.org> - 2018-02-14 21:30 +0100
                Re: Debian part of a version number when epoch is bumped Michael Stone <mstone@debian.org> - 2018-02-14 21:40 +0100
                Re: Debian part of a version number when epoch is bumped Russ Allbery <rra@debian.org> - 2018-02-14 22:00 +0100
                Re: Debian part of a version number when epoch is bumped Michael Stone <mstone@debian.org> - 2018-02-14 22:30 +0100
                Re: Debian part of a version number when epoch is bumped Russ Allbery <rra@debian.org> - 2018-02-14 22:40 +0100
                Re: Debian part of a version number when epoch is bumped Michael Stone <mstone@debian.org> - 2018-02-14 23:10 +0100
                Re: Debian part of a version number when epoch is bumped Russ Allbery <rra@debian.org> - 2018-02-14 23:20 +0100
                Re: Debian part of a version number when epoch is bumped Michael Stone <mstone@debian.org> - 2018-02-14 23:40 +0100
                Re: Debian part of a version number when epoch is bumped Wouter Verhelst <wouter@debian.org> - 2018-02-15 11:20 +0100
                Re: Debian part of a version number when epoch is bumped Simon McVittie <smcv@debian.org> - 2018-02-15 11:50 +0100
                Re: Debian part of a version number when epoch is bumped Wouter Verhelst <wouter@debian.org> - 2018-02-15 12:30 +0100
                Re: Debian part of a version number when epoch is bumped Thibaut Paumard <thibaut@debian.org> - 2018-02-15 13:30 +0100
                Re: Debian part of a version number when epoch is bumped Vincent Ladeuil <v.ladeuil+debian@free.fr> - 2018-02-15 15:10 +0100
                Re: Debian part of a version number when epoch is bumped Guillem Jover <guillem@debian.org> - 2018-02-16 03:10 +0100
                Re: Debian part of a version number when epoch is bumped Dimitri John Ledkov <xnox@debian.org> - 2018-03-12 12:40 +0100
                Re: Debian part of a version number when epoch is bumped Cédric Boutillier <boutil@debian.org> - 2018-03-12 18:50 +0100
                Re: Debian part of a version number when epoch is bumped Simon McVittie <smcv@debian.org> - 2018-02-15 01:00 +0100
                Re: Debian part of a version number when epoch is bumped Michael Stone <mstone@debian.org> - 2018-02-14 21:50 +0100
                Re: Debian part of a version number when epoch is bumped Matt Zagrabelny <mzagrabe@d.umn.edu> - 2018-02-14 21:50 +0100
                Re: Debian part of a version number when epoch is bumped Adam Borowski <kilobyte@angband.pl> - 2018-02-15 08:50 +0100
                Re: Debian part of a version number when epoch is bumped gregor herrmann <gregoa@debian.org> - 2018-02-15 09:00 +0100
                Re: Debian part of a version number when epoch is bumped Adam Borowski <kilobyte@angband.pl> - 2018-02-15 09:30 +0100
                Re: Debian part of a version number when epoch is bumped Thibaut Paumard <thibaut@debian.org> - 2018-02-15 11:20 +0100
                Re: Debian part of a version number when epoch is bumped gregor herrmann <gregoa@debian.org> - 2018-02-15 13:10 +0100
                Re: Debian part of a version number when epoch is bumped Thibaut Paumard <thibaut@debian.org> - 2018-02-15 13:40 +0100
                Re: Debian part of a version number when epoch is bumped Vincent Bernat <bernat@debian.org> - 2018-02-15 14:20 +0100
                Re: Debian part of a version number when epoch is bumped Thibaut Paumard <thibaut@debian.org> - 2018-02-15 15:30 +0100
                Re: Debian part of a version number when epoch is bumped Michael Stone <mstone@debian.org> - 2018-02-15 14:20 +0100
                Re: Debian part of a version number when epoch is bumped Wouter Verhelst <wouter@debian.org> - 2018-02-14 15:50 +0100
                Re: Debian part of a version number when epoch is bumped Raphael Hertzog <hertzog@debian.org> - 2018-02-14 16:10 +0100
                Re: Debian part of a version number when epoch is bumped Andrey Rahmatullin <wrar@debian.org> - 2018-02-14 16:10 +0100
                Re: Debian part of a version number when epoch is bumped Michael Biebl <biebl@debian.org> - 2018-02-14 16:30 +0100
                Re: Debian part of a version number when epoch is bumped Andrey Rahmatullin <wrar@debian.org> - 2018-02-14 17:10 +0100
                Re: Debian part of a version number when epoch is bumped Marc Haber <mh+debian-devel@zugschlus.de> - 2018-02-14 18:30 +0100
                Re: Debian part of a version number when epoch is bumped Wouter Verhelst <wouter@debian.org> - 2018-02-15 11:20 +0100
                Re: Debian part of a version number when epoch is bumped Steve McIntyre <steve@einval.com> - 2018-02-14 15:10 +0100
                Re: Debian part of a version number when epoch is bumped Ian Campbell <ijc@debian.org> - 2018-02-14 15:50 +0100
                Re: Debian part of a version number when epoch is bumped Ian Jackson <ijackson@chiark.greenend.org.uk> - 2018-02-09 19:40 +0100
                Re: Debian part of a version number when epoch is bumped Guillem Jover <guillem@debian.org> - 2018-02-12 03:20 +0100
      Re: Debian part of a version number when epoch is bumped Steve McIntyre <steve@einval.com> - 2018-02-06 14:40 +0100
        Re: Debian part of a version number when epoch is bumped Mattia Rizzolo <mattia@debian.org> - 2018-02-06 15:00 +0100
    Re: Debian part of a version number when epoch is bumped Lars Wirzenius <liw@liw.fi> - 2018-02-06 14:40 +0100
      Re: Debian part of a version number when epoch is bumped Holger Levsen <holger@layer-acht.org> - 2018-02-06 15:20 +0100
      Re: Debian part of a version number when epoch is bumped Jonathan Dowland <jmtd@debian.org> - 2018-02-12 09:40 +0100
    Re: Debian part of a version number when epoch is bumped Jonathan Dowland <jmtd@debian.org> - 2018-02-06 14:40 +0100
      Re: Debian part of a version number when epoch is bumped Mattia Rizzolo <mattia@debian.org> - 2018-02-06 15:00 +0100
        Re: Debian part of a version number when epoch is bumped Chris Lamb <lamby@debian.org> - 2018-02-06 16:20 +0100
          Re: Debian part of a version number when epoch is bumped "Christian T. Steigies" <cts@debian.org> - 2018-02-07 14:00 +0100
            Re: Debian part of a version number when epoch is bumped Ian Jackson <ijackson@chiark.greenend.org.uk> - 2018-02-07 15:00 +0100
              Re: Debian part of a version number when epoch is bumped Ian Campbell <ijc@debian.org> - 2018-02-08 11:20 +0100
                Re: Debian part of a version number when epoch is bumped Raphael Hertzog <hertzog@debian.org> - 2018-02-08 12:00 +0100
                Re: Debian part of a version number when epoch is bumped Ian Campbell <ijc@debian.org> - 2018-02-09 21:00 +0100
                Re: Debian part of a version number when epoch is bumped Chris Lamb <lamby@debian.org> - 2018-02-09 23:10 +0100
            Re: Debian part of a version number when epoch is bumped Colin Watson <cjwatson@debian.org> - 2018-02-07 16:40 +0100
          Re: Debian part of a version number when epoch is bumped Raphael Hertzog <hertzog@debian.org> - 2018-02-07 11:00 +0100
            Re: Debian part of a version number when epoch is bumped Chris Lamb <lamby@debian.org> - 2018-02-07 11:50 +0100
              Re: Debian part of a version number when epoch is bumped Raphael Hertzog <hertzog@debian.org> - 2018-02-07 12:30 +0100
    Re: Debian part of a version number when epoch is bumped Jeremy Bicha <jbicha@debian.org> - 2018-03-28 22:20 +0200
      Re: Debian part of a version number when epoch is bumped Chris Lamb <lamby@debian.org> - 2018-03-29 00:00 +0200
      Re: Debian part of a version number when epoch is bumped Adam Borowski <kilobyte@angband.pl> - 2018-03-29 00:30 +0200
      Re: Debian part of a version number when epoch is bumped Mattia Rizzolo <mattia@debian.org> - 2018-03-29 01:00 +0200
      Re: Debian part of a version number when epoch is bumped "Christian T. Steigies" <cts@debian.org> - 2018-03-29 19:10 +0200
        Re: Debian part of a version number when epoch is bumped Simon McVittie <smcv@debian.org> - 2018-03-29 20:00 +0200
        Re: Debian part of a version number when epoch is bumped Adrian Bunk <bunk@debian.org> - 2018-03-30 13:30 +0200
          Re: Debian part of a version number when epoch is bumped "Christian T. Steigies" <cts@debian.org> - 2018-04-02 20:40 +0200
            Re: Debian part of a version number when epoch is bumped Adrian Bunk <bunk@debian.org> - 2018-04-02 21:10 +0200
            Re: Debian part of a version number when epoch is bumped Simon McVittie <smcv@debian.org> - 2018-04-02 21:50 +0200
              Re: Debian part of a version number when epoch is bumped The Wanderer <wanderer@fastmail.fm> - 2018-04-03 05:10 +0200
                Re: Debian part of a version number when epoch is bumped James McCoy <jamessan@debian.org> - 2018-04-03 05:20 +0200
              Re: Debian part of a version number when epoch is bumped "Christian T. Steigies" <cts@debian.org> - 2018-04-07 20:10 +0200
                Re: Debian part of a version number when epoch is bumped Ian Jackson <ijackson@chiark.greenend.org.uk> - 2018-04-09 15:30 +0200

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