Removed support for git versions older than 2.1

debian oldoldstable has 2.1, and that's what i386ancient uses. It would be
better to require git 2.2, which is needed to use adjusted branches, but
can't do that w/o losing support for some old linux kernels or a
complicated git backport.

Git/CheckAttr.hs

@@ -10,12 +10,11 @@ module Git.CheckAttr where
 import Common
 import Git
 import Git.Command
-import qualified Git.Version
 import qualified Utility.CoProcess as CoProcess
 
 import System.IO.Error
 
-type CheckAttrHandle = (CoProcess.CoProcessHandle, [Attr], Bool, String)
+type CheckAttrHandle = (CoProcess.CoProcessHandle, [Attr], String)
 
 type Attr = String
 
@@ -25,8 +24,7 @@ checkAttrStart :: [Attr] -> Repo -> IO CheckAttrHandle
 checkAttrStart attrs repo = do
 	currdir <- getCurrentDirectory
 	h <- gitCoProcessStart True params repo
-	oldgit <- Git.Version.older "1.7.7"
-	return (h, attrs, oldgit, currdir)
+	return (h, attrs, currdir)
   where
 	params =
 		[ Param "check-attr" 
@@ -36,12 +34,12 @@ checkAttrStart attrs repo = do
 		[ Param "--" ]
 
 checkAttrStop :: CheckAttrHandle -> IO ()
-checkAttrStop (h, _, _, _) = CoProcess.stop h
+checkAttrStop (h, _, _) = CoProcess.stop h
 
 {- Gets an attribute of a file. When the attribute is not specified,
  - returns "" -}
 checkAttr :: CheckAttrHandle -> Attr -> FilePath -> IO String
-checkAttr (h, attrs, oldgit, currdir) want file = do
+checkAttr (h, attrs, currdir) want file = do
 	pairs <- CoProcess.query h send (receive "")
 	let vals = map snd $ filter (\(attr, _) -> attr == want) pairs
 	case vals of
@@ -78,16 +76,9 @@ checkAttr (h, attrs, oldgit, currdir) want file = do
 			else Nothing -- line incomplete
 	numattrs = length attrs
 
-	{- Before git 1.7.7, git check-attr worked best with
-	 - absolute filenames; using them worked around some bugs
-	 - with relative filenames.
-	 - 
-	 - With newer git, git check-attr chokes on some absolute
-	 - filenames, and the bugs that necessitated them were fixed,
-	 - so use relative filenames. -}
-	file'
-		| oldgit = absPathFrom currdir file
-		| otherwise = relPathDirToFileAbs currdir $ absPathFrom currdir file
+	{- git check-attr chokes on some absolute filenames,
+	 - so make sure the filename is relative. -}
+	file' = relPathDirToFileAbs currdir $ absPathFrom currdir file
 	oldattrvalue attr l = end bits !! 0
 	  where
 		bits = split sep l