hashed file storage support code; documentation

 Support code for reading and manipulating hashed file storage (where each file
 and directory is associated with a cryptographic hash, for
 corruption-resistant storage and fast comparisons).
 The supported storage formats include darcs hashed pristine, a plain
 filesystem tree and an indexed plain tree (where the index maintains hashes of
 the plain files and directories).
 .
 This package provides the documentation for a library for the Haskell
 programming language.
 See http://www.haskell.org/ for more information on Haskell.