Unison is a file-synchronization tool for Unix and Windows. It allows two
replicas of a collection of files and directories to be stored on different
hosts (or different disks on the same host), modified separately, and then
brought up to date by propagating the changes in each replica to the other.

Unlike simple mirroring or backup utilities, Unison can deal with updates to
both replicas of a distributed directory structure. Updates that do not
conflict are propagated automatically. Conflicting updates are detected and
displayed.

You need ocaml and lablgtk to compile unison (all of them are provided by 
the slackbuilds project), however none of them are needed to run unison.

Unison allows you to either build a text only binary or a binary that will
use a graphical user interface:

To build the gtk2 graphical inteface binary (the default option): 

    FLAVOR=gtk2 ./unison.SlackBuild 
    or
    ./unison.SlackBuild

To build a textonly binary:

    FLAVOR=text ./unison.SlackBuild