use conversion functions from filepath-bytestring

Behavior should be the same, but I'd hope to eventually get rid of
most of Utility.FileSystemEncoding and this is a first step.

Utility/FileSystemEncoding.hs

@@ -43,6 +43,7 @@ import qualified Data.ByteString.Lazy as L
 import qualified Data.ByteString.UTF8 as S8
 import qualified Data.ByteString.Lazy.UTF8 as L8
 #endif
+import System.FilePath.ByteString (RawFilePath, encodeFilePath, decodeFilePath)
 
 import Utility.Exception
 import Utility.Split
@@ -171,21 +172,11 @@ encodeBL' = L.pack . decodeW8
 encodeBL' = L8.fromString
 #endif
 
-{- Recent versions of the unix package have this alias; defined here
- - for backwards compatibility. -}
-type RawFilePath = S.ByteString
-
-{- Note that the RawFilePath is assumed to never contain NUL,
- - since filename's don't. This should only be used with actual
- - RawFilePaths not arbitrary ByteString that may contain NUL. -}
 fromRawFilePath :: RawFilePath -> FilePath
-fromRawFilePath = decodeBS'
+fromRawFilePath = decodeFilePath
 
-{- Note that the FilePath is assumed to never contain NUL,
- - since filename's don't. This should only be used with actual FilePaths
- - not arbitrary String that may contain NUL. -}
 toRawFilePath :: FilePath -> RawFilePath
-toRawFilePath = encodeBS'
+toRawFilePath = encodeFilePath
 
 {- Converts a [Word8] to a FilePath, encoding using the filesystem encoding.
  -

doc/todo/optimize_by_converting_String_to_ByteString.mdwn

@@ -9,10 +9,7 @@ Benchmarking `git-annex find`, speedups range from 28-66%. The files fly by
 much more snappily. Other commands likely also speed up, but do more work
 than find so the improvement is not as large.
 
-The `bs` branch is in a mergeable state now, except for:
-
-* filepath-bytestring probably has issues with utf16 filenames
-  on Windows. See its TODO.
+The `bs` branch is in a mergeable state now.
 
 Stuff not entirely finished:
 

git-annex.cabal

@@ -320,7 +320,7 @@ Executable git-annex
    directory (>= 1.2),
    disk-free-space,
    filepath,
-   filepath-bytestring,
+   filepath-bytestring (>= 1.4.2.1.1),
    IfElse,
    hslogger,
    monad-logger,

stack.yaml

@@ -24,7 +24,7 @@ extra-deps:
 - sandi-0.5
 - http-client-0.5.14
 - silently-1.2.5.1
-- filepath-bytestring-1.4.2.1.0
+- filepath-bytestring-1.4.2.1.1
 explicit-setup-deps:
   git-annex: true
 resolver: lts-13.29