Align with GNU Tar when a file name is too long

Bug report

Bug description:

Recently I found tarfile may generate a file slightly different with the one made by GNU Tar (https://www.gnu.org/software/tar/), especially when a path name is longer than 100 bytes.

Here's the test code:

# py-tar.py
import tarfile, io
memory_file = io.BytesIO()
tar_obj = tarfile.open(name=None, mode="w", fileobj=memory_file, format=tarfile.GNU_FORMAT)
tar_info = tarfile.TarInfo("abcdef" * 20)
tar_info.type = tarfile.DIRTYPE
tar_info.mode = 0o755
tar_info.mtime = 1609459200  # UTC 2021-01-01
tar_info.uid = 1000
tar_info.gid = 1000
tar_info.uname = "ubuntu"
tar_info.gname = "ubuntu"
tar_obj.addfile(tar_info, None)
tar_obj.close()
memory_file.seek(0)
binary_data = memory_file.read()
# import binascii
# hex_data = binascii.hexlify(binary_data)
# sep = 16
# for i in range(0, len(hex_data), sep * 2):
#     part = hex_data[i:i + sep * 2]
#     print(*(part[i:i+2].decode() for i in range(0, len(part), 2)), binary_data[i//2:][:sep], sep=" ")
with open("py.tar", "wb") as fp:
    fp.write(binary_data)

mkdir -m 755 abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef
tar cf gnu.tar --sort=name --owner=ubuntu:1000 --group=ubuntu:1000 --mtime='UTC 2021-01-01' abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef/
python ./py-tar.py

As a result, when comparing the generated py.tar and gnu.tar, we may get such a difference:

So I wonder will python might align such a detail on tarfile.GNU_FORMAT with the one of GNU tar?

BTW, here's my environment (I'm on Ubuntu 24.04), and I find the main branch of CPython has a similar Lib/tarfile.py and should have a same behavior difference:

$ LANG=C tar --version
tar (GNU tar) 1.35
Copyright (C) 2023 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by John Gilmore and Jay Fenlason.
$ LANG=C python --version
Python 3.12.3

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Linked PRs

• gh-130820

Prüfe zuerst den verknüpften PR gh-130820 und reproduziere anschließend den Unterschied mit dem bereitgestellten Python-Skript und den GNU-Tar-Befehlen. Untersuche Lib/tarfile.py, um die Verarbeitung von GNU_FORMAT für Namen mit mehr als 100 Bytes nachzuverfolgen. Erledigt ist die Aufgabe, wenn das erzeugte Archiv in diesem Fall mit GNU Tar übereinstimmt und an geeigneter Stelle eine Regressionstestabdeckung hinzugefügt wurde.