lib/versioner: Test both spaces and parens in ext versioner paths

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3610

lib/versioner/_external_test/external.bat

@@ -1,5 +1,5 @@
-set FOLDER_PATH=%~1
-set FILE_PATH=%~2
+set "FOLDER_PATH=%~1"
+set "FILE_PATH=%~2"
 echo "1--%FOLDER_PATH%--"
 echo "2--%FILE_PATH%--"
 del "%FOLDER_PATH%\%FILE_PATH%"

lib/versioner/external_test.go

@@ -48,7 +48,7 @@ func TestExternal(t *testing.T) {
 		cmd = `.\_external_test\external.bat`
 	}
 
-	file := "testdata/folder path/long filename.txt"
+	file := "testdata/folder path/dir (parens)/long filename (parens).txt"
 	prepForRemoval(t, file)
 	defer os.RemoveAll("testdata")