Translations:Manual:$wgExternalDiffEngine/6/en

The possible values are:
 * false: wikidiff2 if available, PHP implementation else.
 * wikidiff2: Wikimedia's fast difference engine implemented as a PHP/HHVM module.
 * wikidiff and wikidiff3 are treated as false for backwards compatibility.
 * any other string is treated as a path to external diff executable