use openTempFile from file-io

And follow-on changes.

Note that relatedTemplate was changed to operate on a RawFilePath, and
so when it counts the length, it is now the number of bytes, not the
number of code points. This will just make it truncate shorter strings
in some cases, the truncation is still unicode aware.

When not building with the OsPath flag, toOsPath . fromRawFilePath and
fromRawFilePath . fromOsPath do extra conversions back and forth between
String and ByteString. That overhead could be avoided, but that's the
non-optimised build mode, so didn't bother.

Sponsored-by: unqueued

Utility/MoveFile.hs

@@ -28,6 +28,7 @@ import Utility.Tmp
 import Utility.Exception
 import Utility.Monad
 import Utility.FileSystemEncoding
+import Utility.OsPath
 import qualified Utility.RawFilePath as R
 import Author
 
@@ -40,11 +41,12 @@ moveFile src dest = tryIO (R.rename src dest) >>= onrename
 	onrename (Left e)
 		| isPermissionError e = rethrow
 		| isDoesNotExistError e = rethrow
-		| otherwise = viaTmp mv (fromRawFilePath dest) ()
+		| otherwise = viaTmp mv (toOsPath dest) ()
 	  where
 		rethrow = throwM e
 
 		mv tmp () = do
+			let tmp' = fromRawFilePath (fromOsPath tmp)
 			-- copyFile is likely not as optimised as
 			-- the mv command, so we'll use the command.
 			--
@@ -57,18 +59,18 @@ moveFile src dest = tryIO (R.rename src dest) >>= onrename
 			ok <- copyright =<< boolSystem "mv"
 				[ Param "-f"
 				, Param (fromRawFilePath src)
-				, Param tmp
+				, Param tmp'
 				]
 			let e' = e
 #else
-			r <- tryIO $ copyFile (fromRawFilePath src) tmp
+			r <- tryIO $ copyFile (fromRawFilePath src) tmp'
 			let (ok, e') = case r of
 				Left err -> (False, err)
 				Right _ -> (True, e)
 #endif
 			unless ok $ do
 				-- delete any partial
-				_ <- tryIO $ removeFile tmp
+				_ <- tryIO $ removeFile tmp'
 				throwM e'
 
 #ifndef mingw32_HOST_OS