On December 15, the NetBSD-current tree of NetBSD SUP/FTP server will
switch from NetBSD-1.5 release branch to main trunk, and the
NetBSD-release tree will switch from NetBSD-1.4 release branch to
NetBSD-1.5 release branch.

In other words, after December 15,
- if you SUP NetBSD-current, you will get NetBSD-1.5N (or something)
- if you SUP NetBSD-release, you will get NetBSD-1.5.1_ALPHA

You will likely transfer many files due to this change.
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soda