Can now be built with older git versions (before 1.7.7); the resulting binary should only be used with old git.

Remove git old version check from configure, and use the git version
it was built against in the git check-attr code.

configure.hs

@@ -2,7 +2,6 @@
 
 import System.Directory
 import Data.List
-import Data.String.Utils
 import System.Cmd.Utils
 
 import Build.TestConfig
@@ -11,7 +10,7 @@ tests :: [TestCase]
 tests =
 	[ TestCase "version" getVersion
 	, TestCase "git" $ requireCmd "git" "git --version >/dev/null"
-	, TestCase "git version" checkGitVersion
+	, TestCase "git version" getGitVersion
 	, testCp "cp_a" "-a"
 	, testCp "cp_p" "-p"
 	, testCp "cp_reflink_auto" "--reflink=auto"
@@ -58,25 +57,11 @@ getVersionString = do
 	where
 		middle = drop 1 . init
 
-{- Checks for a new enough version of git. -}
-checkGitVersion :: Test
-checkGitVersion = do
+getGitVersion :: Test
+getGitVersion = do
 	(_, s) <- pipeFrom "git" ["--version"]
 	let version = last $ words $ head $ lines s
-	if dotted version < dotted need
-		then error $ "git version " ++ version ++ " too old; need " ++ need
-		else return $ Config "gitversion" (StringConfig version)
-	where
-		-- for git-check-attr behavior change
-		need = "1.7.7"
-		dotted = sum . mult 1 . reverse . extend 10 . map readi . split "." 
-		extend n l = l ++ replicate (n - length l) 0
-		mult _ [] = []
-		mult n (x:xs) = (n*x) : mult (n*100) xs
-		readi :: String -> Integer
-		readi s = case reads s of
-			((x,_):_) -> x
-			_ -> 0
+	return $ Config "gitversion" (StringConfig version)
 
 {- Set up cabal file with version. -}
 cabalSetup :: IO ()