tar function is breaking symlinks

While debugging the shelve plugin I noticed that the tar function available in the FilePath class is not conserving the symlinks anymore. The shelve plugin is calling the archive function in FilePath:

archive(final ArchiverFactory factory, OutputStream os, final DirScanner scanner) // factory use is TarArchiverFactory with no compression

Both tar archiving function do not properly handle the symlinks to directory (but it works correctly for symlinks to files):

* public int tar(OutputStream out, final String glob) -> uses a DirScanner.Glob (ant style FileSets) that follows the symlink, therefore creates a brand new directory in place of the symlink, not what we want for a tar archive.

* public int tar(OutputStream out, FileFilter filter) -> uses a FileFilter wrapper which for some reasons doesn't redirect the symlink calls to the wrapped FileFilter

Why this is important: this issue has been here for long, but a change made on 2.91 (see my comment below for Issue 2), made this appear more clearly.