[Kde-pim] Focus on stability, LTS branch, transition to frameworks

[John Layt]

We have 3 main components in KDEPIM:

* akonadi
* pimlibs
* apps

Akonadi doesn't use Frameworks and is already Qt5-ready, so doesn't need
any further thought, it can carry-on getting new features as needed.

For pimlibs and apps we have two possible strategies:

1) Split Frameworks and Application releases.  At some point put kdepimlibs
into freeze and start working on the Frameworks split.  Once the split is
done and stabilised enough for a beta release (say after 6-9 months) then
start thinking about porting the apps and getting feedback from that
process.

2) Simultaneous Frameworks and Application releases.  Wait for a convenient
point-in-time, say after KF5.0 and KDE 4.14 releases, and then try to
switch everything over at once.

Option 2 sounds like one big mess to me, it's not really an option is it?
:-)  So it really is just a decision on when pimlibs gets frozen, or
semi-frozen, or whatever.

Let's look at the future release dates, assuming 6 months on from the 4.13
release:

2014-06-01 KF 5.0 Release
2014-08-26 KDE 4.14 Feature Freeze?
2014-10-16 KDE 4.14 Release?
2014-12-01 KF 5.1 Release?

kdepimlibs has already had a lot of Frameworks work done preparing it, some
in current master and some in a frameworks branch, mostly by Steven Kelly,
and the road map is fairly clear.  We also have external users like Plasma
clamouring for some of the libs to use in a Plasma 2014.12 timeframe
(calendar, holidays, etc).  There really is probably not that much work
required to split them, and having a Tech Preview out within 3 months of
starting work is not impossible, with a cleaned-up API and split ready for
beta perhaps 3 months after that.  Some libs could even be moved to KF5
earlier than others, e.g. KHolidays could easily be split and cleaned-up in
time for KF5.1 and Plasma 2014.12, while other more complex libraries wait
for KF5.2 or later.

kdepim apps really shouldn't be thinking about a Frameworks port until the
pimlibs have at least reached Tech Preview or Beta stage, so not for at
least another 3-6 months, which comfortably leaves time for new features
and major improvements in 4.14.  Given the Baloo changes, and the known
issues still with maildir, I believe we need at least 4.14 to provide a
stable solution for users for the 12 months or more while the Frameworks
version is ported.

Even if Laurent is putting new features into pimlibs during 4.14, they
would all be in place before the earliest possible split of pimlibs would
make merging difficult, so I see little obstacle to his doing that.  Once
the split happens though then managing merges becomes a major pain, so
that's the pimlibs4 hard-feature-freeze point.

So, if we were to target a non-split Tech Preview after the 4.14 feature
freeze (2014-09 or 2014-10), that would allow Laurent a 4.14 release before
switching his attention to stabilising PIM Frameworks, and those interested
in frameworks can get to work once 4.13 is released.  The simpler pimlibs
that Plasma wants like KHolidays could target a split and inclusion in KF
5.1, with the rest of pimlibs a first split beta around 2014-12 with a
final release with KF 5.2 (2015-06?), and Applications switching to
Frameworks development using the beta in January 2015.

Thoughts?

John.
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