Commit preview is misleading

[mheap]

I programatically updated a configuration file and when I saw the commit preview I thought that I'd deleted the whole file except the first line

Upon closer inspection, the first line changes, and lines 28 onwards have been removed. This would have been more apparent if unchanged lines were included in the diff (without + or -)

[Wattenberger]

totally true! There's definitely a lot we should do here to make it clearer.