Updating CMake requirement to 2.8.12 RC 1

[Alexander Neundorf]

On Tuesday 27 August 2013, Ben Cooksley wrote:
> On Wed, Aug 28, 2013 at 2:54 AM, Alexander Neundorf <neundorf at kde.org> 
wrote:
> > On Friday 23 August 2013, Ben Cooksley wrote:
> >> On Fri, Aug 23, 2013 at 7:14 PM, David Faure <faure at kde.org> wrote:
> >> > On Friday 23 August 2013 06:51:23 Martin Graesslin wrote:
> >> >> Given that it's already lots of work to keep up with the constant
> >> >> breakage due  to changes in frameworks the outlook of also having
> >> >> breakage in cmake is nothing I look forward to.
> >> > 
> >> > FWIW, I've been using cmake master for many years, and I can't even
> >> > remember *ONE* breakage.
> >> > 
> >> > But anyway, I'm fine with not requiring git master, since the thread
> >> > showed that it's not convenient for everyone.
> >> > 
> >> > I just wanted to refute the argument about "breakages" :)
> >> 
> >> I'll note that build.kde.org has picked up several regressions in the
> >> past, however these were in the CMake "dev" branch, which is expected
> >> to be a little bit more unstable than all the others, as it has been
> >> subject to less testing.
> > 
> > build.kde.org should use the cmake which is required by KF5.
> > If it additionally does builds using cmake from git that's even better.
> 
> It builds it from Git, the 'next' branch to be precise. See
> http://build.kde.org/job/cmake/ for more information.

To make sure KDE builds correctly, which includes that the 
cmake_minimum_required(VERSION x.y.z) are correct, a test build should use the 
minimum required version of cmake IMO.
Otherwise somebody could commit changes to kdelibs, which make use of a new 
feature in cmake, which is not present in the required version, and then the 
build is broken if somebody actually uses the required version.

To make sure new versions of cmake don't break on KDE, ideally a test should 
be added to cmake which builds (parts of) a known working version of kdelibs. 
I tried to do that 3 years ago or so, but didn't get around to finish it.
AFAIK cmake developers would like that, I think for some projects they have 
already something like this.

Alex