[Bug 1857018] Re: apt-get: Can not downgrade dependencies or anything with -t

[David Kalnischkies]

"apt install foo/bar" will try to satisfy dependencies of foo from
release bar if the current candidates do not satisfy the requirements.
That is more a feature for going to a PPA (or backports) than leaving it
and has some issues, but it exists (e.g. your downgrade has probably all
dependencies satisfied by the already installed [newer] versions from
the PPA).

Note that downgrades are still unsupported and can break your system, so
that is really not a painless action. Nobody said activating PPAs left
and right is something you can or should do – or that it is easy to
change your might.

You probably want something like "pick all packages from PPA foo and
install from bar". I think you can express something like that with the
newish patterns, but note that apt doesn't really know if a package was
installed from PPA foo. It guesses that if the current version is the
same as the version in the PPA it was installed from there, but that
isn't the same thing…

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Title:
   apt-get: Can not downgrade dependencies or anything with -t

Status in apt package in Ubuntu:
  Invalid

Bug description:
  Only the latter command downgrades the mythtv-frontend package (after
  removing the PPA from /etc/apt/sources.list.d/ and running 'apt
  update'):

  $ sudo apt-get install mythtv-frontend -s -V -t bionic
  Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  mythtv-frontend is already the newest version (2:30.0+fixes.201912012038.a27754a~ubuntu18.04.1).
  0 upgraded, 0 newly installed, 0 to remove and 8 not upgraded.

  $ sudo apt-get install mythtv-frontend/bionic -s -V
  Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  Selected version '2:29.1+fixes.20180414.329c235-0ubuntu3' (Ubuntu:18.04/bionic [amd64]) for 'mythtv-frontend'
  Suggested packages:
     mythtv-backend (2:29.1+fixes.20180414.329c235-0ubuntu3)
     mythmusic (2:29.1+fixes.20180414.329c235-0ubuntu3)
     mythweather (2:29.1+fixes.20180414.329c235-0ubuntu3)
     mythgallery (2:29.1+fixes.20180414.329c235-0ubuntu3)
     mythgame (2:29.1+fixes.20180414.329c235-0ubuntu3)
  The following packages will be REMOVED:
     mythtv-dbg (2:30.0+fixes.201912012038.a27754a~ubuntu18.04.1)
  The following packages will be DOWNGRADED:
     mythtv-frontend (2:30.0+fixes.201912012038.a27754a~ubuntu18.04.1 => 2:29.1+fixes.20180414.329c235-0ubuntu3)
  0 upgraded, 0 newly installed, 1 downgraded, 1 to remove and 4 not upgraded.
  Remv mythtv-dbg [2:30.0+fixes.201912012038.a27754a~ubuntu18.04.1]
  Inst mythtv-frontend [2:30.0+fixes.201912012038.a27754a~ubuntu18.04.1] (2:29.1+fixes.20180414.329c235-0ubuntu3 Ubuntu:18.04/bionic [amd64])
  Conf mythtv-frontend (2:29.1+fixes.20180414.329c235-0ubuntu3 Ubuntu:18.04/bionic [amd64])

  I do not know, if there is a reason for the different behavior.
  Anyway, I want to be able to easily downgrade the depending packages, too, retaining their auto/manual status.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: apt 1.6.12
  ProcVersionSignature: Ubuntu 5.0.0-37.40~18.04.1-generic 5.0.21
  Uname: Linux 5.0.0-37-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 2.20.9-0ubuntu7.9
  Architecture: amd64
  CurrentDesktop: XFCE
  Date: Thu Dec 19 16:25:51 2019
  InstallationDate: Installed on 2019-05-08 (224 days ago)
  InstallationMedia: Xubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
  SourcePackage: apt
  UpgradeStatus: No upgrade log present (probably fresh install)

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