Please allow snap recipes to pin a source archive

[Michael Terry]

In the recipe used for unity8 snaps [1], we specify the stable-phone-overlay PPA as a source archive. And much like the Touch image builders, we'd like to be able to pin it above the base xenial archive.

Some packages from the overlay get overridden by xenial-updates [2]. This causes subtle bugs and subtle differences based on whether a developer builds locally with a pin vs the launchpad build without a pin.

[1] https://launchpad.net/~unity-team/+snap/unity8-session-silo

[2] An example at the time of this writing is libgstreamer-plugins-bad1.0-0. 1.8.2-1ubuntu0.2 in xenial-updates, 1.8.1-1ubuntu0.2~overlay1 in the overlay. [3]

[3] Actually, we get overridden by 1.8.3 in xenial-proposed. Which we separately don't want enabled for snap builds. (bug 1646145)

[Mattia Rizzolo (mapreri)]

possibly unrelated, but IMHO if packages from xenial-updates are causing bugs not present in xenial (release), then those packages are at fault and shouldn't probably be there (they are regressing).

[Michael Terry (mterry)]

@Mattia, it's not always so simple. Sometimes packages in Touch expect the Touch-version of another package and things don't work right when they aren't both in the repository.

[Michael Terry (mterry)]

Colin and I talked on IRC a bit about this. Colin suggested I try seeing if snapcraft wanted to add direct support for pinning instead. So I filed bug 1654304 about that.

[Pat McGowan (pat-mcgowan)]

mark incomplete pending results via snapcraft