Some handy Template Haskell splices for including the current git hash and branch in the code of your project. Useful for including in panic messages, --version output, or diagnostic info for more informative bug reports.

{-# LANGUAGE TemplateHaskell #-}
import Development.GitRev

panic :: String -> a
panic msg = error panicMsg
  where panicMsg =
          concat [ "[panic ", $(gitBranch), "@", $(gitHash)
                 , " (", $(gitCommitDate), ")"
                 , " (", $(gitCommitCount), " commits in HEAD)"
                 , dirty, "] ", msg ]
        dirty | $(gitDirty) = " (uncommitted files present)"
              | otherwise   = ""

main = panic "oh no!"

% cabal exec runhaskell Example.hs
Example.hs: [panic master@2ae047ba5e4a6f0f3e705a43615363ac006099c1 (Mon Jan 11 11:50:59 2016 -0800) (14 commits in HEAD) (uncommitted files present)] oh no!