text/x-diff mime type for mutt usage

[bob@xxxxxxxxxx (Bob Proulx)]

I sometimes see people attach diffs and patch files as a mime type
text/x-diff.  This seems to be a freedesktop.org initiative.
(Personally I prefer them as plain text in the message.  A lot of
mailing lists reject or strip attachments.)

My mailcap does not know about this and so mutt does not either.  I
see the following:

  [-- Attachment #2: some-name-here.patch --]
  [-- Type: text/x-diff, Encoding: 7bit, Size: 1.3K --]

  [-- text/x-diff is unsupported (use 'v' to view this part) --]

  [-- Attachment #3 --]
  [-- Type: text/plain, Encoding: 7bit, Size: 0.1K --]

What mailcap entry would I need to make that view as text inline in
mutt?  Or would that need to be a mutt configuration?

It has been a while since I have tinkered with mailcap.  Any pointers
to a good mailcap tutorial or howto would be appreciated.

Thanks
Bob