TODO:
+ lockfile
+ md5 checksums
+ recovery from lost 'latest' symlink
+ testing

for v0.9

- make a snapshot of any filesystem (local, nfs...)

for v1.0

- make separate "incremental directory" (for dump to tape)

Make a note about related projects:
http://www.pegasys.ws/dirvish/	dirvish - rsync to remote disk, perl
http://freshmeat.net/projects/farsync/