TL;DR: I want to read the source code of LuaTeX. How and where?
I want to know exactly how the Knuth-Plass algorithm for line breaking is implemented in LuaTeX. Not an explanation, I want the source. The Lua callback for the algorithm is
tex.linebreak. I downloaded the "source" from https://serveur-svn.lri.fr/svn/modhel/luatex and searched for
linebreak throughout all files; it only occurs in a data structure declaration. Even more annoying, I couldn't even find where is the source for the LuaTeX engine. I am of course assumming LuaTeX is open source, but after two days looking for it, go figure