avoid using Utility.Path.AbsRel in Utility.Path.Windows

AbsRel depends on unix, but Utility.Path.Windows will be used in some
libraries that are part of the setup-depends, which cannot depend on
unix.

The only reason that AbsRel uses getWorkingDirectory on unix is that
it returns RawFilePath. getCurrentDirectory returns FilePath and so
needs a conversion to RawFilePath. Looks like a newer version of
directory will fix that, by using OsPath, so eventually AbsPath should
be able to switch to using getCurrentDirectory on unix, and then the
small code duplication in this commit won't be needed.

Sponsored-by: Dartmouth College's Datalad project

Utility/Path/Windows.hs

@@ -12,11 +12,13 @@ module Utility.Path.Windows (
 	convertToWindowsNativeNamespace
 ) where
 
-import Utility.Path.AbsRel
+import Utility.Path
+import Utility.FileSystemEncoding
 
-import System.FilePath.ByteString (RawFilePath)
+import System.FilePath.ByteString (RawFilePath, combine)
 import qualified Data.ByteString as B
 import qualified System.FilePath.Windows.ByteString as P
+import System.Directory (getCurrentDirectory)
 
 {- Convert a filepath to use Windows's native namespace.
  - This avoids filesystem length limits.
@@ -34,7 +36,8 @@ convertToWindowsNativeNamespace f
 	| otherwise = do
 		-- Make absolute because any '.' and '..' in the path
 		-- will not be resolved once it's converted.
-		p <- absPath f
+		cwd <- toRawFilePath <$> getCurrentDirectory
+		let p = simplifyPath (combine cwd f)
 		-- Normalize slashes.
 		let p' = P.normalise p
 		return (win32_file_namespace <> p')