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 restrictions go away.
Therefore we now change to use only two components for the feature
level and use the scheme:
<major>.<minor>.<patch>[-rc<n>] = Release
<major>.<minor>.<date>[-<id>] = Development
Describe the meaning of each version component in more detail in the
documentation of CMAKE_VERSION. Simplify the per-component version
variable documentation by referencing the main variable.
Include information about how to compare version strings. Also add
an historical note about the version scheme used prior to commit
v2.8.2~105^2~4 (New version scheme to support branchy workflow,
2010-04-23).
Chuck Atkins
Brad King
Kitware Robot