[quietbritishjim]

Why do this? Why not choose a minimum version that has the features your build system depends on and just leave the first line at the top?

It's not like you can use features from the newer version anyway, if you seriously want to support the older version. And if the same line of code has two different meanings in two versions, you want the old meaning (as you would get without target_version(<new version>)) because presumably you wrote your CMakeLists assuming that behaviour.

Edit: If I had read TFA before I posted I would've seen that's where the quoted code comes from. As the first thing that it teaches you to put in your CMakeLists.txt that is a pretty unfortunate failure IMO. If an old version of CMake has a behaviour you don't want (such as "wrong linking behavior on macOS" quoted in the linked article) then bite the bullet and use a newer minimum version of CMake. You could do this on only the cases it would cause a problem (e.g. just on MacOS, or just when a cache variable is set) but do so unconditionally of the version, so if someone tries to use an old version of CMake in that configuration they'll get a hard error. That's what you want!