git diff extensions (except rename) are unsupported

[hannesm]

this needs to be done for "use this patch instead of gnu patch in opam"

[hannesm]

There's now:

type git_ext =
  | Rename_only of string * string
  | Delete_only
  | Create_only

So, I guess these are supported. Will close this issue. Please reopen and mention which other extensions are needed.