Csup is a rewrite of CVSup in C.

CVSup is a software for distributing and updating collections of
files accross a network.  It can efficiently and accurately mirror
all types of files, including sources, binaries, hard links, symbolic
links, and even device nodes.  In addition to being a great
general-purpose mirroring tool, CVSup includes special features and
optimizations specifically tailored to CVS repositories.

Csup only supports checkout mode.