What the author wants is git blame with highlights. IntelliJ does this very good. On the margin to your left you can see the age of each line. Recent changes -

What the author wants is git blame with highlights. IntelliJ does this very good. On the margin to your left you can see the age of each line. Recent changes - the one you are reviewing - will be be bright white, while older proven code more faded. All inside the already powerful editor you need to navigate bigger pieces of code. Except that will not show you removed lines. Forget it, just use the diff feature.