I think it would be useful if IDEs allowed a team to share when multiple people are editing the same file at the same time. And even get notified when such a change gets committed so you merge it right away. And I don't mean just watching the repo.

Sometimes two people are working separately on the same bug when they could be collaborating. Its also easier to merge changes one by one, instead of dealing with 10 at once. And if a change is completely incompatible, its best to deal with that when the code is committed, not a week later.

It would also be cool if there were chat integrated with that, with a history that gets linked when you commit so you can understand the context later.