GitLab

Historically CMake used three version components for the feature level.
We released new features while incrementing only the third version
component.  Since commit v2.8.2~105^2~4 (New version scheme to support
branchy workflow, 2010-04-23) we used the fourth version component for
bug-fix releases and the development date:

 <major>.<minor>.<patch>[.<tweak>][-rc<n>] = Release
 <major>.<minor>.<patch>.<date>[-<id>]     = Development

This solidified use of three components for the feature level, and was
necessary to continue releasing 2.x versions because:

* Some existing projects performed floating-point comparisons of
  ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION} to 2.x numbers
  so ``x`` could never be higher than 9.

* Version 2.9.<date> was used briefly in post-2.8.0 development in
  CVS prior to the transition to Git, so using it in releases may
  have caused confusion.

Now that we are moving to 3.x versions, these two restriction...