Consider a file like "package foobar; func DoFoo() { ... }; func DoBar() { ... }". You then refactor that to two packages, "package foo; func Do() { ... }" "package bar; func Do() { ... }". The body of foobar.DoFoo is identical to foo.Do, but no version control system I've ever used will move the history of that function body to the new location.

I guess what I'm saying that tracking renames as a first-class object is nice, but it still doesn't represent many types of refactorings. To smugly declare perfection, a version control system should probably have that feature, because it is a relatively common refactoring.