Darcs: primitive patches version 3

by Petr Ročkai for haskell.org

Darcs, a revision control system, uses so-called patches to represent changes to individual version-controlled files, where the "primitive" patches are the lowest level of this representation, capturing notions like "hunks" (akin to what diff(1) produces), token replace and file and directory addition/removal. I propose to implement a different representation of these primitive patches, hoping to improve both performance and flexibility of darcs and to facilitate future development.