As I recall, git5 was such a piece of junk that they deleted it so nobody could use it any more. It had its fans but they were all deluded. It was a demonstrated fact that git5 users were less productive than normal g4 users.

What is/was "git5"? Git the vcs is only about to release version 3.0... Googling only reveals some gene that happens to be named that...

It was a way to pretend that you were using git when you were in fact using piper.

it’s an old google internal interface over google’s vcs piper that let you use git to manage your changes

The big problem with it was that you had to specify upfront which directories you will be editing, and only those were cloned locally. Later if you wanted to add a quick debug printout somewhere else, you would spend 20 minutes tracking more directories and merging / rebasing branches. All because git choked on the huge monorepo.