go:generate line ended up in the package doc

[tv42]

https://github.com/ajankovic/xdiff/blob/8d005d68cfa77d98b42e6a9b25334a2c54a6e034/xdiff.go#L1-L5

The go:generate line needs to be moved out from the package doc comment. A whitespace-separated line below package xdiff, or similarly whitespace-separated line just above the type it's operating on, are the common places.