[Mediawiki-l] page history: revision diff

[Farkas, Illes]

Dear All,

I've downloaded the dump file enwiki-pages-meta-history and extracted
the <text> of each page revision. Do you happen to know what
program/script Mediawiki uses to find the text marked with red on a
diff page like this:

http://en.wikipedia.org/w/index.php?title=American_Samoa&diff=261185809&oldid=252441574

Thanks and a Happy New Year to everyone.