debugging improvements

add timestamps to debug messages

Add lots of debug output in the assistant's threads.

Assistant/Common.hs

@@ -0,0 +1,21 @@
+{- Common infrastructure for the git-annex assistant threads.
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Assistant.Common (
+	module X,
+	ThreadName,
+	debug
+) where
+
+import Common.Annex as X
+
+import System.Log.Logger
+
+type ThreadName = String
+
+debug :: ThreadName -> [String] -> IO ()
+debug threadname ws = debugM threadname $ unwords $ (threadname ++ ":") : ws