git-mailinfo munges the patch?

I noticed that the new mailinfo when splitting a message into
cover letter and the patch text seems to munge the patch text,
applying the same "if content-type is not there then assume
latin-1 and recode to utf-8" logic that is applied to the commit
log message.  That munging should not be done to the patch text,
and it appears the current code botches it.

I am a bit too busy with day job today and haven't had a chance
to look into this problem fully, but 1.5.0.3 does not seem to
have this problem but post 87ab7992 mailinfo is problematic.