Repos use {bookid}.txt as the filename of the actual book in the repos

[sethwoodworth]

This is the way that books came from PG. Ideally, the filenames would be titled something based on the author and/or title of the book. But I haven't decided on the right syntax, nor on how to handle this change in a way that is backwards compatible with PG's current repo structure. This is something that I would eventually like to fix, but would like some sort of consensus about what to migrate to before we do so.

For now, keeping the bookid allows a script to easily find the right book file to act on.

[sethwoodworth]

Unfortunately, symlinks are not a universal solution