Mimetype text/x-patch (.patch and .diff)
A proposal icon:

Related to #2334

PR?
Another idea should be just the red and green lines:

PR?
IMO, Yes please 馃榾
This looks good @Jupiter007-43
I wonder if a slightly dark color for the patch would work better, but I can test that myself if you make the PR ;)
10% darker:

The PR use the first colors.