Improve `tarfile` streaming mode to handle very large archives

Bug report

Bug description:

I am trying to use tarfile to write very large archives, and the process is being killed by the OOM killer. I would expect+want to be able to use it in streaming mode (write an unlimited number of files) like the standard tar command line utility supports by default.

Reproduction case attached.

import gc
import io
import os
import psutil
import tarfile

if __name__ == "__main__":
    t = tarfile.open("a.tar", mode="w") # default compresslevel 9
    for i in range(1,100_000_000):
        if i % 10_000 == 0:
            gc.collect()
            process = psutil.Process(os.getpid())
            mem_info = process.memory_info()
            mem = mem_info.rss
            print(f"Iteration {i}, memory usage: {mem}")

        bs = (" "*1000 + str(i)).encode('utf8')
        with io.BytesIO(bs) as file:
            tarinfo = tarfile.TarInfo(name="cool_files/{i}.txt")
            tarinfo.size = len(bs)
            t.addfile(tarinfo, file)

The memory usage increases without bound because the list of this line in addfile():

self.members.append(tarinfo)

I'm not sure what the use-case is for this line. In write-only mode, it does not seem useful. Maybe mixed read/write? But in general it does not seem correct to assume you can fit all the tarinfo's in memory.

Edit: As a workaround, I'm setting t.members=[] manually.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

从 tarfile 中 TarFile.addfile() 附近的实现以及 self.members.append(tarinfo) 这一行开始，使用报告中的复现来观察内存增长。确定 write-only 或 streaming 模式的预期行为，然后验证写入超大归档时内存使用量能够保持在有界范围内，同时不会破坏 tarfile 的其他使用场景。