Opening backports pre-release

[Evan Broder]

Greetings, Tech Board -
  The backports team has been playing with a proposal for about a year
now that we'd like to finally submit to you folks.

Currently, during the period between FeatureFreeze and release (about
1/3 of the cycle!), it's impossible to upload either new packages or
new features to Ubuntu (freeze exceptions excluded). Post-release,
this is an issue already addressed by the backports process. We'd like
to propose extending the use of backports by opening the backports
pocket for uploads and Debian syncs at FeatureFreeze, and then copying
the contents of the backports pocket to the x+1 release when it opens,
similar to what we do already for SRUs.

We would still enforce the current backports requirements (the package
must "build, install, and run", any reverse-dependencies must still
work with the new package, and all uploads must be approved by a
backporter). These requirements are stronger than those for general
archive uploads, so we don't believe that there is significant risk to
post-release archive quality of x+1.

I see a handful of potential issues with this, and I only have answers
for some of them, so if the TB is generally interested in the idea,
I'd certainly appreciate feedback and suggestions:

 - Skew between backports (and therefore x+1) and the main archive:
bugfixes in release not making it into backports, versions in release
superseding those in backports, etc. In general, I think we would want
a mechanism to invalidate packages in the backports pocket whenever
that package is uploaded to the release pocket, and possibly to the
proposed pocket, though I don't know what that is.

 - Archive admin workload. All backports currently require some action
from archive admins. For no-source-change uploads, an archive admin
runs a script on the archive master. For source-change uploads,
because they are uploaded post-release, they are automatically put
into the unapproved queue. Additionally, new packages have to go
through sourceNEW and binNEW. Our proposal would create additional
work for the archive admins near release time, which may be
problematic.

 - Upload privileges. I believe that currently anybody on ~ubuntu-dev
can upload any package to the backports pocket, and backporters can
approve backports of packages they otherwise would not be able to
upload. The backports team would prefer to maintain that - would it be
sufficient to ensure that manual backports uploads always go through
unapproved?

 - Component isolation. All packages in the backports pocket build
with all components enabled. This means that if we copy binaries to
x+1, we could be copying binaries built against packages from the
wrong component. It might make sense to only pocket copy source
packages into the x+1 release, instead of all packages.

If the TB approves this, the backports team would gladly take
responsibility for proposing patches to Launchpad, ubuntu-dev-tools,
ubuntu-archive-tools, and anything else we've forgotten that needs
modification to support the new workflow.

I know this is rather late notice, but I'll go ahead and add this to
tomorrow's meeting agenda in the hopes that there's time to discuss
it. I'm also generally available for in-person or IRC discussion.

Thanks,