compile git revision info into Haskell projects

 Ths package provides some handy Template Haskell splices for including the
 current git hash and branch in the code of your project.
 .
 This is useful for including in panic messages, --version output, or
 diagnostic info for more informative bug reports.
 .
 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.