Why does cvsup + supfile delete all my ports ?

[Lowell Gilbert]

Quoting the handbook:

       When specifying a tag in CVSup's configuration file, it must be
       preceded with tag= (RELENG_4 will become tag=RELENG_4). Keep in mind
       that only the tag=. is relevant for the ports collection.

So don't use the RELENG_4 tag for ports; use '.' instead.