So if anyone wants to adopt those, complete or just parts, just take
them. As for Portage, Zac has practically already filled my role.

So I guess that wraps it up. It's been a nice ride most of the time,
but now it's time for me to leave the Gentoo train.

The second new feature is that package sets can now be (re)defined on the emerge command line. This is done using the following syntax:
emerge '@setname{key1=value1,key2=value2}'
where setname can either be an existing package set, or a new one to define a set without having to modify any files. Note the quotes that are necessary to ensure that emerge gets the argument as-is without interference from the shell. The nice thing is this syntax also works inside set expressions. The not-so-nice thing is that for now there are a few restrictions about the values you can use, as there is no quoting mechanism implemented yet (this is planned however). So using any of the following characters or whitespace inside the braces will lead to undefined behavior: { } @ = ,
Another restriction is that you may not redefine package sets that are created by a multiset section in sets.conf (as those use different options that only make sense when defining multiple sets at once).
Note that for redefining existing package sets you only have to pass those options that should be different from the sets.conf definition.

And last but not least, to make the above features a bit easier to use there is also a new DummyPackageSet class that can be used to build a package set only by using operators, and/or to include a few packages without having to edit an external file. So it's even easier than before to define a new set @world-without-system, using
[world-without-system]
class=portage.sets.base.DummyPackageSet
extend=world
remove=system

This feature is just a few minutes old, so it will probably be extended or otherwise changed in the future. Current restrictions include

• strict left-to-right evaluation order
• only defined package sets can be used as operands (no package names)
• feature is currently only available on the commandline, not via sets.conf

And while I'm on it, I've also added a new AgeSet class to select installed packages that are older/newer than a given number of days.

Please see the shipped NEWS and RELEASE-NOTES for changes from the 2.1
series, and check bugs.gentoo.org before reporting issues in
#gentoo-portage.

Note for Ebuild developers: This test release includes a partially
rewritten version of repoman that's not heavily tested, so do not use
it for committing anything to the tree and double check its reports
with other tools or a 2.1 version.

Marius

• The most important new things will be package sets. Sounds boring at first, I know, but due to a flexible framework they allow us (and you) to do interesting things, like eventually replacing glsa-check and revdep-rebuild (while the security set is pretty much identical to what glsa-check did, the set for rebuilding packages with broken linkage is very experimental, incomplete and not enabled by default yet). Or simply update or remerge all packages in a specific category. And that's not even touching the power of the CommandOutputSet class
• Support for GLEP 42 news, as an alternative for package maintainers to the elog framework
• Visibility filtering based on licenses, aka ACCEPT_LICENSE, which allows you for example to build a RMS-approved system and will render the interactive license prompts currently found in some packages obsolete
• A new FEATURES flag to keep libraries that are still used on a soname change, including a simply way to rebuild all packages using the old library (using another package set). A bit too late for the expat issue, but hopefully it helps to prevent future incidents of that kind
• And of course all the things that already appeared in portage-2.1.3

But no light without darkness, there will be some important changes requiring your attention:

• While not set in stone yet, the behavior of system and world will likely change to match that of other package set and single packages. Currently emerge world is the same as emerge --noreplace world, meaning that installed packages aren't rebuilt (unlike emerge $foo which will rebuild $foo). With 2.2 emerge world is likely going to be the same as emerge $(< /var/lib/portage/world), if you want the old behavior you'll have to use --noreplace. That change also has other benefits beyond consistency, like removing the restriction that world/system could not be combined with other packages on the commandline.
• "world" will likely no longer include "system", if you want to update both you'll have to specify both
• Due to a change in the namespace many portage related tools will require an update or generate a lot of deprecation warnings.

As said, it's just a preview, and some things are still work in progress, but it should give you a first impression what portage-2.2 will be about. I think we might create the first test releases in late November, but that's no promise. Though if you want to test it you don't have to wait that long, just install subversion and read http://www.gentoo.org/proj/en/portage/doc/testing.xml (that's especially recommended for maintainers of portage related tools), just don't expect everything to work perfectly yet.

- should they simply act like aliases for multiple packages? E.g.
should `emerge -C sets/kde` be equivalent to `emerge -C kdepkg1 kdepkg2
kdepkg3 ...`? Or does the behavior need to be "smarter" in some ways?

- what kind of atoms should be supported in sets? Simple and versioned
atoms for sure, but what about complex atoms (use-conditional, any-of,
blockers)?

- should sets be supported everywhere, or only in selected use cases?
(everywhere would include depstrings for example)

- what use cases are there for package sets? Other than the established
"system" and "world", and the planned "all" and "security" sets.

- how/where should sets be stored/distributed?