trusted=yes sources are secure, we just don't know why

trusted=yes sources are secure, we just don't know why

Do not require a special flag to be present to update trusted=yes
sources as this flag in the sources.list is obviously special enough.

Note that this is just disabling the error message, the user will still
be warned about all the (possible) failures the repository generated, it
is just triggering the acceptance of the warnings on a source-by-source
level.

Similarily, the trusted=no flag doesn't require the user to pass
additional flags to update, if the repository looks fine in the view of
apt it will update just fine. The unauthenticated warnings will "just" be
presented then the data is used.

In case you wonder: Both was the behavior in previous versions, too.