Updates to the DragonFly source code is performed using cvsup. cvsup compares your local system source or ports files to a remote repository, and downloads any changes. Only the differences in the files are downloaded, saving on bandwidth and time.
cvsup exists as a port (devel/cvsup) and traditionally had to be installed separately on FreeBSD. With DragonFly, the binary is installed as part of the base system.
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