[cmake-developers] RFC: add version to project() call

[Alexander Neundorf]

Hi,

on cmake stage I have a simple branch AddVersionToProjectCommand.
This extends the project command to also accept a version number:

project(Foo VERSION 1.2.3 CXX)

All that does is setting some more variables (beside PROJECT_NAME, 
PROJECT_SOURCE_DIR, PROJECT_BINARY_DIR and the <projectName>_... equivalents).

When setting a version, you also get PROJECT_VERSION and 
PROJECT_VERSION_(MAJOR|MINOR|PATCH|TWEAK) variables as well as the 
<projectName>_... equivalents.

These version variables can then be used in other commands/macros/functions 
which need a version.
I modified write_basic_package_version_file() accordingly, so that you can now 
simply do

project(Foo VERSION 1.2.3)

...

write_basic_package_version_file(FooConfigVersion.cmake
                                 COMPATIBILITY AnyNewerVersion)

and this will use the version number from the project() call automatically (if 
no VERSION has been given explicitely).

Comments ?

Alex