add build time and git info to BuildInfo

src/compiler/GF/Infra/BuildInfo.hs

@@ -1,13 +1,35 @@
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE TemplateHaskell #-}
+
 module GF.Infra.BuildInfo where
 import System.Info
 import Data.Version(showVersion)
 
+import Language.Haskell.TH.Syntax
+import Control.Monad.IO.Class
+import Control.Exception
+import Data.Time
+import Data.Time.Format.ISO8601
+import System.Process
+
+-- Use Template Haskell to get compile time
+buildTime :: String
+buildTime = $(do
+                 timeZone <- liftIO getCurrentTimeZone
+                 time <- liftIO $ utcToLocalTime timeZone <$> getCurrentTime
+                 return $ LitE $ StringL $ iso8601Show time )
+
+-- Use Template Haskell to get current Git information
+gitInfo :: String
+gitInfo = $(do
+               info <- liftIO $ try $ readProcess "git" ["log", "--format=\"Commit %h Tag %(describe:tags=true)\"", "-1"] "" :: Q (Either SomeException String)
+               return $ LitE $ StringL $ either (\_ -> "unavailable") id info )
+
 {-# NOINLINE buildInfo #-}
 buildInfo =
     "Built on "++os++"/"++arch
-    ++" with "++compilerName++"-"++showVersion compilerVersion
-    ++", flags:"
+    ++" with "++compilerName++"-"++showVersion compilerVersion ++ " at " ++ buildTime ++ "\nGit info: " ++ gitInfo
+    ++"\nFlags:"
 #ifdef USE_INTERRUPT
     ++" interrupt"
 #endif