remove windows --git-dir unix style path hack

This is no longer necessary, at least with msysgit 1.8.5.2.msysgit.0.
Its root cause may have been fixed by other recent git path fixes.
It was causing the webapp to fail to make repos on other drives.

Git/Command.hs

@@ -25,18 +25,10 @@ gitCommandLine :: [CommandParam] -> Repo -> [CommandParam]
 gitCommandLine params r@(Repo { location = l@(Local _ _ ) }) =
 	setdir : settree ++ gitGlobalOpts r ++ params
   where
-	setdir = Param $ "--git-dir=" ++ gitpath (gitdir l)
+	setdir = Param $ "--git-dir=" ++ gitdir l
 	settree = case worktree l of
 		Nothing -> []
 		Just t -> [Param $ "--work-tree=" ++ gitpath t]
-#ifdef mingw32_HOST_OS
-	-- despite running on windows, msysgit wants a unix-formatted path
-	gitpath s
-		| absoluteGitPath s = "/" ++ dropDrive (toInternalGitPath s)
-		| otherwise = s
-#else
-	gitpath = id
-#endif
 gitCommandLine _ repo = assertLocal repo $ error "internal"
 
 {- Runs git in the specified repo. -}