Edit conflict resolution assistance

[greenrd]

A colleague edited the notes of a story. I had added a bunch of tasks at the same time, and when I tried to save my changes, a red error bar appeared saying that another person had edited the story, which is great (thanks for implementing that!) but it doesn't help me to fix it. It was unclear whether the changes had been merged (they hadn't) or whether it was just my changes being shown (it was).

One thing I really like about Wikipedia editing is that if there is an edit conflict, they show a diff so that you can see the difference between the other person's new version and your new version. Well, in practice I find it a bit confusing, but in principle it seems like a good idea to show both versions.