RecipeAppendVersionNumberToInstallpath

In some situations, it's necessary to keep older versions of a program along with the newer. Here is a recipe for appending the version number to your install path:

IF(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
    SET(ORIGINAL_INSTALL_PREFIX ${CMAKE_INSTALL_PREFIX} CACHE STRING "Default prefix path" FORCE)
ENDIF()
MARK_AS_ADVANCED(ORIGINAL_INSTALL_PREFIX)

IF( NOT( VERSION VERSION_EQUAL PROJECT_VERSION) )
    SET(CMAKE_INSTALL_PREFIX "${ORIGINAL_INSTALL_PREFIX}-${VERSION}" CACHE STRING "Install path" FORCE)
    SET(PROJECT_VERSION ${VERSION})
ENDIF()

This ensures that the CMAKE_INSTALL_PREFIX is updated whenever the old version number and the new version number doesn't match. This does have some side-effects, such as situations where the user is customizing the CMAKE_INSTALL_PREFIX to some custom location. Such users would need to modify the ORIGINAL_INSTALL_PREFIX instead to ensure that the project is going to the desired place.

The CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT is necessary here because if it's missing, the path becomes recursive and will continue to append ${PROJECT_NAME}-${VERSION} to the path infinitely. The conditional ensures that it only does this once.