@dancingtreefrog beyondcompare from scootersoftware, but it is not for free and not opensource, I am using it since 1997, it is very reliable and synchronizes even large files (> 2 GByte) or many files (> 100.000) without any problems, even over poor internet connections e.g. via ftp. Most tools crash with those requests. It has a simple scripting engine also.

#filecomparison #foldercomparison #textcomparison #synchronisation #backup