cmake: hoist cmake version to cmake.mk

[tcberner]

Summary

The version of the cmake port has been scattered in four ports.
This change moves the version to a single point: cmake.mk, which now
exposes it as _CMAKE_VERSION. It also got a new _internal argument
to mask away all the other magic it does for devel/cmake to be able
to include it.

• devel/cmake, devel/cmake-gui, devel/cmake-doc:

use DISTVERISON=${_CMAKE_VERSION}
let cmake.mk handle MASTER_SITES

• devel/kms-cmake-utils:

use ${_CMAKE_VERSION_R} as PLIST_SUB

[lbartoletti]

LGTM
Thanks!

[rene]

Mk/Uses/cmake.mk

62

171

Why not use DISTVERSION twice here instead of DISTVERSION and PORTVERSION ?

[adridg]

The internal variable _CMAKE_VERSION should probably be mentioned somewhere in cmake.mk -- it's not a tunable variable, but it is used by ports (e.g. kms-cmake-utils) and should therefore have documentation.

Mk/Uses/cmake.mk

20

# _internal             Not to be used by any other ports than the ones created from the 
#                       release-tarball of cmake (i.e. devel/cmake).

62

# Only devel/cmake should set argument '_internal'. If it is not set, depend on devel/cmake
# and introduce the knobs for a build-with-CMake port.

171

That seems to have been copied from the devel/cmake/Makefile and has been that way for some time; you are right that it seems weirdly inconsistent.