Display exception message when a transfer fails due to an exception.

For example, I had a copy to a remote that was failing for an unknown
reason. This let me see the exception was createDirectory: permission
denied; the underlying problem being a permissions issue.

Annex/Transfer.hs

@@ -106,7 +106,8 @@ runTransfer t file shouldretry a = do
 		v <- tryAnnex run
 		case v of
 			Right b -> return b
-			Left _ -> do
+			Left e -> do
+				warning (show e)
 				b <- getbytescomplete metervar
 				let newinfo = oldinfo { bytesComplete = Just b }
 				if shouldretry oldinfo newinfo

debian/changelog

@@ -7,6 +7,7 @@ git-annex (5.20140718) UNRELEASED; urgency=medium
     Fix this, including support for fixing up repositories that
     were incompletely repaired before.
   * Fix cost calculation for non-encrypted remotes.
+  * Display exception message when a transfer fails due to an exception.
 
  -- Joey Hess <joeyh@debian.org>  Mon, 21 Jul 2014 14:41:26 -0400