here is a diff

  lang=diff
  @@ derp derp @@
  x
  y

  - x
  - y
  + z

derp derp
~~~~~~~~~~

here is a diff

@@ derp derp @@
x
y

- x
- y
+ z

derp derp
~~~~~~~~~~
here is a diff

  @@ derp derp @@
  x
  y
  
  - x
  - y
  + z

derp derp
