PartialCode dir is looking for last hard-coded forward-slash in Windows OS

At constructor of PartialCode.java, in line 23, the slash it looks for is hard-coded to be forward-slash (Used everywhere except Windows):

protected PartialCode(TemplateContext tc, DefaultMustacheFactory df, Mustache mustache, String type, String variable) {
    super(tc, df, mustache, variable, type);

    // Use the  name of the parent to get the name of the partial
    String file = tc.file();
    int dotindex = file.lastIndexOf(".");
    extension = dotindex == -1 ? "" : file.substring(dotindex);
    int slashindex = file.lastIndexOf("/");    <------------------------------ line 23
    dir = file.substring(0, slashindex + 1);
    recrusionLimit = df.getRecursionLimit();
}

When running on Windows OS, the file's path is usually stored using back-slashes and .lastIndexOf("/") will fail to find the correct index.

Open PartialCode.java and inspect the PartialCode constructor around line 23, starting with how tc.file() is parsed into the parent directory. Reproduce the issue with a Windows-style path and verify that the resulting directory is correct on both Windows and non-Windows paths; done means the relevant path separator is handled without breaking existing behavior.