> if you do want to have a breaking new version, what exactly do you do?
You change the name. Like "Raku" instead of "Perl6". Once you've reached a certain level of stability and usage, any substantial breaking change is going to inevitably result in a fork, so embracing that up front is going to result in a much better experience.
Yeah, I like Rich Hickey’s critique of semantic versioning. Major version changes just overload the name and cause confusion: if you must break compatibility, fork and rename.
You change the name of the software, like consoles? The next big Gnome version could then be called Gnome 360 followed by Gnome 1, Gnome 64 or Gnome 3.11 for work groups.
Improve existing stuff, add new stuff. That can be done with backwards compatibility if you have a well defined API. I haven't looked at Gnome's API in years so I'm not sure what's its state, but one shining example for this is Redis which is backwards compatible to 11 years ago.
Another great and more relevant example is browsers.
You change the name. Like "Raku" instead of "Perl6". Once you've reached a certain level of stability and usage, any substantial breaking change is going to inevitably result in a fork, so embracing that up front is going to result in a much better experience.