close handle so windows can stat the file

windows cannot stat a file that another process has open, which caused
this to crash with an exception

Remote/Directory.hs

@@ -404,6 +404,7 @@ storeExportWithContentIdentifierM dir src _k loc overwritablecids p =
 		withTmpFileIn destdir template $ \tmpf tmph -> do
 			liftIO $ withMeteredFile src p (L.hPut tmph)
 			liftIO $ hFlush tmph
+			liftIO $ hClose tmph
 			liftIO (getFileStatus tmpf) >>= liftIO . mkContentIdentifier tmpf >>= \case
 				Nothing -> 
 					return $ Left "unable to generate content identifier"

doc/bugs/windows_fails_import_export_tests.mdwn

@@ -9,6 +9,9 @@ remote.
 
 No indication of why it failed.
 
+> Update: Now it shows the problem, which is that the exported file is
+> locked so statting it fails. --[[Joey]]
+
 The second test fails in an import. It gets as far as updating foo/master,
 but then when it tries to merge that branch, there's a merge conflict.
 That merge conflict seems very likely due to being on an adjusted branch;