Manual:$wgExternalDiffEngine

Details
Name of the external diff engine to use, or false to use the internal engine.

The possible value are:
 * wikidiff: Use external C++ wikidiff>Special:MyLanguage/Extension:wikidiff|wikidiff module from the extensions package.
 * wikidiff2: Use external C++ wikidiff2>Special:MyLanguage/Extension:wikidiff2|wikidiff2 module from the extensions package.
 * wikidiff3: Use internal PHP wikidiff3>Special:MyLanguage/Manual:WikiDiff3.php|wikidiff3 class.
 * other value: Use this value as the command line that generates the diff result.

This setting replaces useextdiff>Special:MyLanguage/Manual:$wgUseExternalDiffEngine|$wgUseExternalDiffEngine.