venv: activate.fish breaks prompt (prints directory) due to "echo 'exit $old_status' | ." line

Bug report

Bug description:

python3 -m venv test
source test/bin/activate.fish

causes ls-like output on every command.

Fix in venv/scripts/common/activate.fish:

        # Output the original/"old" prompt.
        _old_fish_prompt
        # Restore the return status of the previous command.
       return $old_status

fish, version 4.1.2

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-144558
• gh-150936

使用 python3 -m venv test 和 source test/bin/activate.fish 重現問題，然後檢查 venv/scripts/common/activate.fish 中提示字元還原與回傳狀態處理附近的程式碼。將提議的變更與連結的 PR gh-144558 和 gh-150936 進行比較；完成的標準是啟用環境時不再列印類似目錄的輸出，同時保留上一個指令的狀態。