Bug#852967: release-notes: Document apt pinning changes

[Julian Andres Klode]

Package: release-notes
Severity: normal

In apt 1.1, we introduced a new pinning engine. The old one assigned one
pin priority per package, the new assigns pin priorities per version and
then picks the version with the highest pin that is (not a downgrade||has
a pin > 1000).

I think it is reasonable to mention this as this changes the effect of
some pins, especially negative ones: Previously, pinning a version to -1
effectively prevented the package from being installed (the package pin
was -1), it now only prevents the version from being installed.

For example given icedove 1:45.6.0-2 and 1:45.6.0-3, pinning the latter version
to -1 with:

Package: icedove
Pin: version 1:45.6.0-3
Pin-Priority: -1

changed like that:
<<EOF
$ LD_LIBRARY_PATH=/var/lib/schroot/chroots/jessie-amd64/usr/lib/x86_64-linux-gnu/ /var/lib/schroot/chroots/jessie-amd64/usr/bin/apt-cache policy icedove
icedove:
Installed: (none)
Candidate: (none)
Package pin: 1:45.6.0-3
Version table:
1:45.6.0-3 -1
100 http://deb.debian.org/debian/ experimental/main amd64 Packages
1:45.6.0-2 -1
900 http://deb.debian.org/debian/ unstable/main amd64 Packages
500 http://deb.debian.org/debian/ testing/main amd64 Packages
***@jak-x230:~/Projects/Debian/apt:master$ apt-cache policy icedove
icedove:
Installed: (none)
Candidate: 1:45.6.0-2
Version table:
1:45.6.0-3 -1
100 http://deb.debian.org/debian experimental/main amd64 Packages
100 http://deb.debian.org/debian experimental/main i386 Packages
1:45.6.0-2 900
900 http://deb.debian.org/debian unstable/main amd64 Packages
500 http://deb.debian.org/debian testing/main amd64 Packages
EOF

-> There is a candidate now, as you'd expect it to. Also note that the output
now shows proper per-version pin values, and the Package Pin field is gone.

There may be some other subtle changes in some more corner cases.

But the implementation now matches the description in the manual page
and thus does what people expect from it, so that is a huge step
forward. I don't have any detailed wording ready, but I hope the
information is sufficient.

PS. apt does not really require InRelease files as 5.3.2.2 says (it's only
the spec in the wiki that says it's required).

-- System Information:
Debian Release: stretch/sid
APT prefers unstable
APT policy: (900, 'unstable'), (500, 'unstable-debug'), (500, 'buildd-unstable'), (500, 'testing'), (100, 'experimental'), (1, 'experimental-debug')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.8.0-2-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_IE.UTF-8, LC_CTYPE=en_IE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)

[Baptiste Jammet]

Hi,

Post by Julian Andres Klode
In apt 1.1, we introduced a new pinning engine.

[...]

Is the attached snippet (from your words) clear enough?
I dropped the examples as I think pin-players will understand easily
(I'm not one but I understood, so...).

Please comment if needed. Thanks

Baptiste

[Debian Bug Tracking System]

Your message dated Thu, 27 Apr 2017 14:14:52 +0200
with message-id <***@mailoo.org>
and subject line Re: Bug#852967: release-notes: Document apt pinning changes
has caused the Debian Bug report #852967,
regarding release-notes: Document apt pinning changes
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
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