DVCS vs. Subversion brittleness (was Re: Moving to D)

[Ulrik Mikaelsson]

2011/2/16 Russel Winder <russel at russel.org.uk>:
>
> Definitely the case.  There can only be one repository that represents
> the official state of a given project.  That isn't really the issue in
> the move from CVCS systems to DVCS systems.
>
Just note that not all projects have a specific "state" to represent.
Many projects are centered around the concept of a centralized
project, a "core"-team, and all-around central organisation and
planning. Some projects however, I guess the Linux kernel is a prime
example, have been quite de-centralized even in their nature for a
long time.

In the case of KDE, for a centralized example, there is a definite
"project version", which is the version currently blessed by the
central project team. There is a centralized project planning,
including meetings, setting out goals for the coming development.

In the case of Linux, it's FAR less obvious. Sure, most people see
master at torvalds/linux-2.6.git as THE Linux-version. However, there are
many other trees interesting to track as well, such as the various
distribution-trees which might incorporate many drivers not in
mainline, especially for older stability-oriented kernels, RHEL or
Debian is probably THE version to care about. You might also be
interested in special-environment-kernels, such as non x86-kernels, in
which case you're probably more interested in the central repo for
that architecture, which is rarely Linuses. Also, IIRC, hard and soft
realtime-enthusiasts neither looks at linuses tree first.

Above all, in the Linux-kernel, there is not much of "centralised
planning". Linus doesn't call to a big planning-meeting quarterly to
set up specific milestones for the next kernel release, but in the
beginning of each cycle, he is spammed with things already developed
independently, scratching someones itch. He then cherry-picks the
things that has got good reviews and are interesting for where he
wants to go with the kernel. That is not to say that there aren't a
lot of coordination and communication, but there isn't a clear
centralized authority steering development in the same ways as in many
other projects.

The bottom line is, many projects, even ones using DVCS, are often
centrally organized. However, the Linux kernel is clear evidence it is
not the only project model that works.