From Guiffy Software:
Guiffy is a visual file compare diff tool, folder compare, and merge tool and component. Guiffy is a cross-platform application available on Windows, MacOS, Linux and Unix. Downloads are packaged as InstallAnywhere kits to make setup a snap. Guiffy can be used to compare/merge source files of any type (with builtin UNICODE, MBCS, and over 150 File Encoding formats support). Guiffy also provides sophisticated folder and file tree compare and synchronization capabilities. Plus, a command line interface is included for use in scripts and integration with CM/SCM systems (Including: CVS, Perforce, and StarBase). Guiffy's 3-way smart merge, called SureMerge, surpasses all other merge tools with its intelligent functionality and ease-of-use. And, Guiffy comes with a Java API package so you can use it as a component in your Java applications.