Add file path to the header in TaildirSource

After using TaildirSource to collect log data, I found that there is no file path in the flume event.
Though TaildirSource supports add customed header value like this : a1.sources.r1.headers.f1.headerKey1 = value1,
we can't add file path to the header when the filegroup path contains regex expression.File path is necessary to locate the log data.