I added a node to magit.texi that documents magit-interactive-rebase and rebase-mode. I don't really know anything about TexInfo, so I just cargo-culted all the commands and I haven't tested to see if the file is syntactically correct. Feel free to edit for syntactic correctness, factual correctness, and writing style in order to make it fit with the rest of the manual. (Or tell me what you want changed and I'll do it.)
This should fix #443.
Add texinfo doc for "Magit-interactive-rebase".
Add TOC entry for Interactive Rebasing node